pyarrow.Table#
- class pyarrow.Table#
Bases:
pyarrow.lib._PandasConvertible
A collection of top-level named, equal length Arrow arrays.
Warning
Do not call this class’s constructor directly, use one of the
from_*
methods instead.Examples
>>> import pyarrow as pa >>> n_legs = pa.array([2, 4, 5, 100]) >>> animals = pa.array(["Flamingo", "Horse", "Brittle stars", "Centipede"]) >>> names = ["n_legs", "animals"]
Construct a Table from arrays:
>>> pa.Table.from_arrays([n_legs, animals], names=names) pyarrow.Table n_legs: int64 animals: string ---- n_legs: [[2,4,5,100]] animals: [["Flamingo","Horse","Brittle stars","Centipede"]]
Construct a Table from a RecordBatch:
>>> batch = pa.record_batch([n_legs, animals], names=names) >>> pa.Table.from_batches([batch]) pyarrow.Table n_legs: int64 animals: string ---- n_legs: [[2,4,5,100]] animals: [["Flamingo","Horse","Brittle stars","Centipede"]]
Construct a Table from pandas DataFrame:
>>> import pandas as pd >>> df = pd.DataFrame({'year': [2020, 2022, 2019, 2021], ... 'n_legs': [2, 4, 5, 100], ... 'animals': ["Flamingo", "Horse", "Brittle stars", "Centipede"]}) >>> pa.Table.from_pandas(df) pyarrow.Table year: int64 n_legs: int64 animals: string ---- year: [[2020,2022,2019,2021]] n_legs: [[2,4,5,100]] animals: [["Flamingo","Horse","Brittle stars","Centipede"]]
Construct a Table from a dictionary of arrays:
>>> pydict = {'n_legs': n_legs, 'animals': animals} >>> pa.Table.from_pydict(pydict) pyarrow.Table n_legs: int64 animals: string ---- n_legs: [[2,4,5,100]] animals: [["Flamingo","Horse","Brittle stars","Centipede"]] >>> pa.Table.from_pydict(pydict).schema n_legs: int64 animals: string
Construct a Table from a dictionary of arrays with metadata:
>>> my_metadata={"n_legs": "Number of legs per animal"} >>> pa.Table.from_pydict(pydict, metadata=my_metadata).schema n_legs: int64 animals: string -- schema metadata -- n_legs: 'Number of legs per animal'
Construct a Table from a list of rows:
>>> pylist = [{'n_legs': 2, 'animals': 'Flamingo'}, {'year': 2021, 'animals': 'Centipede'}] >>> pa.Table.from_pylist(pylist) pyarrow.Table n_legs: int64 animals: string ---- n_legs: [[2,null]] animals: [["Flamingo","Centipede"]]
Construct a Table from a list of rows with pyarrow schema:
>>> my_schema = pa.schema([ ... pa.field('year', pa.int64()), ... pa.field('n_legs', pa.int64()), ... pa.field('animals', pa.string())], ... metadata={"year": "Year of entry"}) >>> pa.Table.from_pylist(pylist, schema=my_schema).schema year: int64 n_legs: int64 animals: string -- schema metadata -- year: 'Year of entry'
Construct a Table with
pyarrow.table()
:>>> pa.table([n_legs, animals], names=names) pyarrow.Table n_legs: int64 animals: string ---- n_legs: [[2,4,5,100]] animals: [["Flamingo","Horse","Brittle stars","Centipede"]]
- __init__(*args, **kwargs)#
Methods
__init__
(*args, **kwargs)add_column
(self, int i, field_, column)Add column to Table at position.
append_column
(self, field_, column)Append column at end of columns.
cast
(self, Schema target_schema, bool safe=True)Cast table values to another schema.
column
(self, i)Select a column by its column name, or numeric index.
combine_chunks
(self, MemoryPool memory_pool=None)Make a new table by combining the chunks this table has.
drop
(self, columns)Drop one or more columns and return a new table.
drop_null
(self)Remove missing values from a Table.
equals
(self, Table other, ...)Check if contents of two tables are equal.
field
(self, i)Select a schema field by its column name or numeric index.
filter
(self, mask[, null_selection_behavior])Select rows from the table.
flatten
(self, MemoryPool memory_pool=None)Flatten this Table.
from_arrays
(arrays[, names, schema, metadata])Construct a Table from Arrow arrays.
from_batches
(batches, Schema schema=None)Construct a Table from a sequence or iterator of Arrow RecordBatches.
from_pandas
(type cls, df, Schema schema=None)Convert pandas.DataFrame to an Arrow Table.
from_pydict
(mapping[, schema, metadata])Construct a Table from Arrow arrays or columns.
from_pylist
(mapping[, schema, metadata])Construct a Table from list of rows / dictionaries.
get_total_buffer_size
(self)The sum of bytes in each buffer referenced by the table.
group_by
(self, keys)Declare a grouping over the columns of the table.
itercolumns
(self)Iterator over all columns in their numerical order.
join
(self, right_table, keys[, right_keys, ...])Perform a join between this table and another one.
remove_column
(self, int i)Create new Table with the indicated column removed.
rename_columns
(self, names)Create new table with columns renamed to provided names.
replace_schema_metadata
(self[, metadata])Create shallow copy of table by replacing schema key-value metadata with the indicated new metadata (which may be None), which deletes any existing metadata.
select
(self, columns)Select columns of the Table.
set_column
(self, int i, field_, column)Replace column in Table at position.
slice
(self[, offset, length])Compute zero-copy slice of this Table.
sort_by
(self, sorting)Sort the table by one or multiple columns.
take
(self, indices)Select rows from the table.
to_batches
(self[, max_chunksize])Convert Table to a list of RecordBatch objects.
to_pandas
(self[, memory_pool, categories, ...])Convert to a pandas-compatible NumPy array or DataFrame, as appropriate
to_pydict
(self)Convert the Table to a dict or OrderedDict.
to_pylist
(self)Convert the Table to a list of rows / dictionaries.
to_reader
(self[, max_chunksize])Convert the Table to a RecordBatchReader.
to_string
(self, *[, show_metadata, preview_cols])Return human-readable string representation of Table.
unify_dictionaries
(self, ...)Unify dictionaries across all chunks.
validate
(self, *[, full])Perform validation checks.
Attributes
Names of the table's columns.
List of all columns in numerical order.
Total number of bytes consumed by the elements of the table.
Number of columns in this table.
Number of rows in this table.
Schema of the table and its columns.
Dimensions of the table: (#rows, #columns).
- add_column(self, int i, field_, column)#
Add column to Table at position.
A new table is returned with the column added, the original table object is left unchanged.
- Parameters
- Returns
Table
New table with the passed column added.
Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'n_legs': [2, 4, 5, 100], ... 'animals': ["Flamingo", "Horse", "Brittle stars", "Centipede"]}) >>> table = pa.Table.from_pandas(df)
Add column:
>>> year = [2021, 2022, 2019, 2021] >>> table.add_column(0,"year", [year]) pyarrow.Table year: int64 n_legs: int64 animals: string ---- year: [[2021,2022,2019,2021]] n_legs: [[2,4,5,100]] animals: [["Flamingo","Horse","Brittle stars","Centipede"]]
Original table is left unchanged:
>>> table pyarrow.Table n_legs: int64 animals: string ---- n_legs: [[2,4,5,100]] animals: [["Flamingo","Horse","Brittle stars","Centipede"]]
- append_column(self, field_, column)#
Append column at end of columns.
- Parameters
- Returns
Table
New table with the passed column added.
Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'n_legs': [2, 4, 5, 100], ... 'animals': ["Flamingo", "Horse", "Brittle stars", "Centipede"]}) >>> table = pa.Table.from_pandas(df)
Append column at the end:
>>> year = [2021, 2022, 2019, 2021] >>> table.append_column('year', [year]) pyarrow.Table n_legs: int64 animals: string year: int64 ---- n_legs: [[2,4,5,100]] animals: [["Flamingo","Horse","Brittle stars","Centipede"]] year: [[2021,2022,2019,2021]]
- cast(self, Schema target_schema, bool safe=True)#
Cast table values to another schema.
- Parameters
- Returns
Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'n_legs': [2, 4, 5, 100], ... 'animals': ["Flamingo", "Horse", "Brittle stars", "Centipede"]}) >>> table = pa.Table.from_pandas(df) >>> table.schema n_legs: int64 animals: string -- schema metadata -- pandas: '{"index_columns": [{"kind": "range", "name": null, "start": 0, "' + 509
Define new schema and cast table values:
>>> my_schema = pa.schema([ ... pa.field('n_legs', pa.duration('s')), ... pa.field('animals', pa.string())] ... ) >>> table.cast(target_schema=my_schema) pyarrow.Table n_legs: duration[s] animals: string ---- n_legs: [[2,4,5,100]] animals: [["Flamingo","Horse","Brittle stars","Centipede"]]
- column(self, i)#
Select a column by its column name, or numeric index.
- Parameters
- Returns
Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'n_legs': [2, 4, 5, 100], ... 'animals': ["Flamingo", "Horse", "Brittle stars", "Centipede"]}) >>> table = pa.Table.from_pandas(df)
Select a column by numeric index:
>>> table.column(0) <pyarrow.lib.ChunkedArray object at ...> [ [ 2, 4, 5, 100 ] ]
Select a column by its name:
>>> table.column("animals") <pyarrow.lib.ChunkedArray object at ...> [ [ "Flamingo", "Horse", "Brittle stars", "Centipede" ] ]
- column_names#
Names of the table’s columns.
Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'n_legs': [2, 4, 5, 100], ... 'animals': ["Flamingo", "Horse", "Brittle stars", "Centipede"]}) >>> table = pa.Table.from_pandas(df) >>> table.column_names ['n_legs', 'animals']
- columns#
List of all columns in numerical order.
- Returns
list
ofChunkedArray
Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'n_legs': [None, 4, 5, None], ... 'animals': ["Flamingo", "Horse", None, "Centipede"]}) >>> table = pa.Table.from_pandas(df) >>> table.columns [<pyarrow.lib.ChunkedArray object at ...> [ [ null, 4, 5, null ] ], <pyarrow.lib.ChunkedArray object at ...> [ [ "Flamingo", "Horse", null, "Centipede" ] ]]
- combine_chunks(self, MemoryPool memory_pool=None)#
Make a new table by combining the chunks this table has.
All the underlying chunks in the ChunkedArray of each column are concatenated into zero or one chunk.
- Parameters
- memory_pool
MemoryPool
, defaultNone
For memory allocations, if required, otherwise use default pool.
- memory_pool
- Returns
Examples
>>> import pyarrow as pa >>> n_legs = pa.chunked_array([[2, 2, 4], [4, 5, 100]]) >>> animals = pa.chunked_array([["Flamingo", "Parrot", "Dog"], ["Horse", "Brittle stars", "Centipede"]]) >>> names = ["n_legs", "animals"] >>> table = pa.table([n_legs, animals], names=names) >>> table pyarrow.Table n_legs: int64 animals: string ---- n_legs: [[2,2,4],[4,5,100]] animals: [["Flamingo","Parrot","Dog"],["Horse","Brittle stars","Centipede"]] >>> table.combine_chunks() pyarrow.Table n_legs: int64 animals: string ---- n_legs: [[2,2,4,4,5,100]] animals: [["Flamingo","Parrot","Dog","Horse","Brittle stars","Centipede"]]
- drop(self, columns)#
Drop one or more columns and return a new table.
- Parameters
- Returns
Table
New table without the columns.
- Raises
KeyError
If any of the passed columns name are not existing.
Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'n_legs': [2, 4, 5, 100], ... 'animals': ["Flamingo", "Horse", "Brittle stars", "Centipede"]}) >>> table = pa.Table.from_pandas(df)
Drop one column:
>>> table.drop(["animals"]) pyarrow.Table n_legs: int64 ---- n_legs: [[2,4,5,100]]
Drop more columns:
>>> table.drop(["n_legs", "animals"]) pyarrow.Table ... ----
- drop_null(self)#
Remove missing values from a Table. See
pyarrow.compute.drop_null()
for full usage.Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'year': [None, 2022, 2019, 2021], ... 'n_legs': [2, 4, 5, 100], ... 'animals': ["Flamingo", "Horse", None, "Centipede"]}) >>> table = pa.Table.from_pandas(df) >>> table.drop_null() pyarrow.Table year: double n_legs: int64 animals: string ---- year: [[2022,2021]] n_legs: [[4,100]] animals: [["Horse","Centipede"]]
- equals(self, Table other, bool check_metadata=False)#
Check if contents of two tables are equal.
- Parameters
- other
pyarrow.Table
Table to compare against.
- check_metadatabool, default
False
Whether schema metadata equality should be checked as well.
- other
- Returns
Examples
>>> import pyarrow as pa >>> n_legs = pa.array([2, 2, 4, 4, 5, 100]) >>> animals = pa.array(["Flamingo", "Parrot", "Dog", "Horse", "Brittle stars", "Centipede"]) >>> names=["n_legs", "animals"] >>> table = pa.Table.from_arrays([n_legs, animals], names=names) >>> table_0 = pa.Table.from_arrays([]) >>> table_1 = pa.Table.from_arrays([n_legs, animals], ... names=names, ... metadata={"n_legs": "Number of legs per animal"}) >>> table.equals(table) True >>> table.equals(table_0) False >>> table.equals(table_1) True >>> table.equals(table_1, check_metadata=True) False
- field(self, i)#
Select a schema field by its column name or numeric index.
Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'n_legs': [2, 4, 5, 100], ... 'animals': ["Flamingo", "Horse", "Brittle stars", "Centipede"]}) >>> table = pa.Table.from_pandas(df) >>> table.field(0) pyarrow.Field<n_legs: int64> >>> table.field(1) pyarrow.Field<animals: string>
- filter(self, mask, null_selection_behavior='drop')#
Select rows from the table.
See
pyarrow.compute.filter()
for full usage.- Parameters
- mask
Array
orarray-like
The boolean mask to filter the table with.
- null_selection_behavior
How nulls in the mask should be handled.
- mask
- Returns
- filtered
Table
A table of the same schema, with only the rows selected by the boolean mask.
- filtered
Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'year': [2020, 2022, 2019, 2021], ... 'n_legs': [2, 4, 5, 100], ... 'animals': ["Flamingo", "Horse", "Brittle stars", "Centipede"]}) >>> table = pa.Table.from_pandas(df)
Define a mask and select rows:
>>> mask=[True, True, False, None] >>> table.filter(mask) pyarrow.Table year: int64 n_legs: int64 animals: string ---- year: [[2020,2022]] n_legs: [[2,4]] animals: [["Flamingo","Horse"]] >>> table.filter(mask, null_selection_behavior='emit_null') pyarrow.Table year: int64 n_legs: int64 animals: string ---- year: [[2020,2022,null]] n_legs: [[2,4,null]] animals: [["Flamingo","Horse",null]]
- flatten(self, MemoryPool memory_pool=None)#
Flatten this Table.
Each column with a struct type is flattened into one column per struct field. Other columns are left unchanged.
- Parameters
- memory_pool
MemoryPool
, defaultNone
For memory allocations, if required, otherwise use default pool
- memory_pool
- Returns
Examples
>>> import pyarrow as pa >>> struct = pa.array([{'n_legs': 2, 'animals': 'Parrot'}, ... {'year': 2022, 'n_legs': 4}]) >>> month = pa.array([4, 6]) >>> table = pa.Table.from_arrays([struct,month], ... names = ["a", "month"]) >>> table pyarrow.Table a: struct<animals: string, n_legs: int64, year: int64> child 0, animals: string child 1, n_legs: int64 child 2, year: int64 month: int64 ---- a: [ -- is_valid: all not null -- child 0 type: string ["Parrot",null] -- child 1 type: int64 [2,4] -- child 2 type: int64 [null,2022]] month: [[4,6]]
Flatten the columns with struct field:
>>> table.flatten() pyarrow.Table a.animals: string a.n_legs: int64 a.year: int64 month: int64 ---- a.animals: [["Parrot",null]] a.n_legs: [[2,4]] a.year: [[null,2022]] month: [[4,6]]
- static from_arrays(arrays, names=None, schema=None, metadata=None)#
Construct a Table from Arrow arrays.
- Parameters
- arrays
list
ofpyarrow.Array
orpyarrow.ChunkedArray
Equal-length arrays that should form the table.
- names
list
ofstr
, optional Names for the table columns. If not passed, schema must be passed.
- schema
Schema
, defaultNone
Schema for the created table. If not passed, names must be passed.
- metadata
dict
or Mapping, defaultNone
Optional metadata for the schema (if inferred).
- arrays
- Returns
Examples
>>> import pyarrow as pa >>> n_legs = pa.array([2, 4, 5, 100]) >>> animals = pa.array(["Flamingo", "Horse", "Brittle stars", "Centipede"]) >>> names = ["n_legs", "animals"]
Construct a Table from arrays:
>>> pa.Table.from_arrays([n_legs, animals], names=names) pyarrow.Table n_legs: int64 animals: string ---- n_legs: [[2,4,5,100]] animals: [["Flamingo","Horse","Brittle stars","Centipede"]]
Construct a Table from arrays with metadata:
>>> my_metadata={"n_legs": "Number of legs per animal"} >>> pa.Table.from_arrays([n_legs, animals], ... names=names, ... metadata=my_metadata) pyarrow.Table n_legs: int64 animals: string ---- n_legs: [[2,4,5,100]] animals: [["Flamingo","Horse","Brittle stars","Centipede"]] >>> pa.Table.from_arrays([n_legs, animals], ... names=names, ... metadata=my_metadata).schema n_legs: int64 animals: string -- schema metadata -- n_legs: 'Number of legs per animal'
Construct a Table from arrays with pyarrow schema:
>>> my_schema = pa.schema([ ... pa.field('n_legs', pa.int64()), ... pa.field('animals', pa.string())], ... metadata={"animals": "Name of the animal species"}) >>> pa.Table.from_arrays([n_legs, animals], ... schema=my_schema) pyarrow.Table n_legs: int64 animals: string ---- n_legs: [[2,4,5,100]] animals: [["Flamingo","Horse","Brittle stars","Centipede"]] >>> pa.Table.from_arrays([n_legs, animals], ... schema=my_schema).schema n_legs: int64 animals: string -- schema metadata -- animals: 'Name of the animal species'
- static from_batches(batches, Schema schema=None)#
Construct a Table from a sequence or iterator of Arrow RecordBatches.
- Parameters
- batchessequence or iterator of
RecordBatch
Sequence of RecordBatch to be converted, all schemas must be equal.
- schema
Schema
, defaultNone
If not passed, will be inferred from the first RecordBatch.
- batchessequence or iterator of
- Returns
Examples
>>> import pyarrow as pa >>> n_legs = pa.array([2, 4, 5, 100]) >>> animals = pa.array(["Flamingo", "Horse", "Brittle stars", "Centipede"]) >>> batch = pa.record_batch([n_legs, animals], names=names) >>> batch.to_pandas() n_legs animals 0 2 Flamingo 1 4 Horse 2 5 Brittle stars 3 100 Centipede
Construct a Table from a RecordBatch:
>>> pa.Table.from_batches([batch]) pyarrow.Table n_legs: int64 animals: string ---- n_legs: [[2,4,5,100]] animals: [["Flamingo","Horse","Brittle stars","Centipede"]]
Construct a Table from a sequence of RecordBatches:
>>> pa.Table.from_batches([batch, batch]) pyarrow.Table n_legs: int64 animals: string ---- n_legs: [[2,4,5,100],[2,4,5,100]] animals: [["Flamingo","Horse","Brittle stars","Centipede"],["Flamingo","Horse","Brittle stars","Centipede"]]
- from_pandas(type cls, df, Schema schema=None, preserve_index=None, nthreads=None, columns=None, bool safe=True)#
Convert pandas.DataFrame to an Arrow Table.
The column types in the resulting Arrow Table are inferred from the dtypes of the pandas.Series in the DataFrame. In the case of non-object Series, the NumPy dtype is translated to its Arrow equivalent. In the case of object, we need to guess the datatype by looking at the Python objects in this Series.
Be aware that Series of the object dtype don’t carry enough information to always lead to a meaningful Arrow type. In the case that we cannot infer a type, e.g. because the DataFrame is of length 0 or the Series only contains None/nan objects, the type is set to null. This behavior can be avoided by constructing an explicit schema and passing it to this function.
- Parameters
- df
pandas.DataFrame
- schema
pyarrow.Schema
, optional The expected schema of the Arrow Table. This can be used to indicate the type of columns if we cannot infer it automatically. If passed, the output will have exactly this schema. Columns specified in the schema that are not found in the DataFrame columns or its index will raise an error. Additional columns or index levels in the DataFrame which are not specified in the schema will be ignored.
- preserve_indexbool, optional
Whether to store the index as an additional column in the resulting
Table
. The default of None will store the index as a column, except for RangeIndex which is stored as metadata only. Usepreserve_index=True
to force it to be stored as a column.- nthreads
int
, defaultNone
If greater than 1, convert columns to Arrow in parallel using indicated number of threads. By default, this follows
pyarrow.cpu_count()
(may use up to system CPU count threads).- columns
list
, optional List of column to be converted. If None, use all columns.
- safebool, default
True
Check for overflows or other unsafe conversions.
- df
- Returns
Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'n_legs': [2, 4, 5, 100], ... 'animals': ["Flamingo", "Horse", "Brittle stars", "Centipede"]}) >>> pa.Table.from_pandas(df) pyarrow.Table n_legs: int64 animals: string ---- n_legs: [[2,4,5,100]] animals: [["Flamingo","Horse","Brittle stars","Centipede"]]
- static from_pydict(mapping, schema=None, metadata=None)#
Construct a Table from Arrow arrays or columns.
- Parameters
- Returns
Examples
>>> import pyarrow as pa >>> n_legs = pa.array([2, 4, 5, 100]) >>> animals = pa.array(["Flamingo", "Horse", "Brittle stars", "Centipede"]) >>> pydict = {'n_legs': n_legs, 'animals': animals}
Construct a Table from a dictionary of arrays:
>>> pa.Table.from_pydict(pydict) pyarrow.Table n_legs: int64 animals: string ---- n_legs: [[2,4,5,100]] animals: [["Flamingo","Horse","Brittle stars","Centipede"]] >>> pa.Table.from_pydict(pydict).schema n_legs: int64 animals: string
Construct a Table from a dictionary of arrays with metadata:
>>> my_metadata={"n_legs": "Number of legs per animal"} >>> pa.Table.from_pydict(pydict, metadata=my_metadata).schema n_legs: int64 animals: string -- schema metadata -- n_legs: 'Number of legs per animal'
- static from_pylist(mapping, schema=None, metadata=None)#
Construct a Table from list of rows / dictionaries.
- Parameters
- Returns
Examples
>>> import pyarrow as pa >>> n_legs = pa.array([2, 4, 5, 100]) >>> animals = pa.array(["Flamingo", "Horse", "Brittle stars", "Centipede"]) >>> pylist = [{'n_legs': 2, 'animals': 'Flamingo'}, ... {'year': 2021, 'animals': 'Centipede'}]
Construct a Table from a list of rows:
>>> pa.Table.from_pylist(pylist) pyarrow.Table n_legs: int64 animals: string ---- n_legs: [[2,null]] animals: [["Flamingo","Centipede"]]
Construct a Table from a list of rows with pyarrow schema:
>>> my_schema = pa.schema([ ... pa.field('year', pa.int64()), ... pa.field('n_legs', pa.int64()), ... pa.field('animals', pa.string())], ... metadata={"year": "Year of entry"}) >>> pa.Table.from_pylist(pylist, schema=my_schema).schema year: int64 n_legs: int64 animals: string -- schema metadata -- year: 'Year of entry'
- get_total_buffer_size(self)#
The sum of bytes in each buffer referenced by the table.
An array may only reference a portion of a buffer. This method will overestimate in this case and return the byte size of the entire buffer.
If a buffer is referenced multiple times then it will only be counted once.
Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'n_legs': [None, 4, 5, None], ... 'animals': ["Flamingo", "Horse", None, "Centipede"]}) >>> table = pa.Table.from_pandas(df) >>> table.get_total_buffer_size() 76
- group_by(self, keys)#
Declare a grouping over the columns of the table.
Resulting grouping can then be used to perform aggregations with a subsequent
aggregate()
method.- Parameters
- Returns
See also
Examples
>>> import pandas as pd >>> import pyarrow as pa >>> df = pd.DataFrame({'year': [2020, 2022, 2021, 2022, 2019, 2021], ... 'n_legs': [2, 2, 4, 4, 5, 100], ... 'animal': ["Flamingo", "Parrot", "Dog", "Horse", ... "Brittle stars", "Centipede"]}) >>> table = pa.Table.from_pandas(df) >>> table.group_by('year').aggregate([('n_legs', 'sum')]) pyarrow.Table n_legs_sum: int64 year: int64 ---- n_legs_sum: [[2,6,104,5]] year: [[2020,2022,2021,2019]]
- itercolumns(self)#
Iterator over all columns in their numerical order.
- Yields
Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'n_legs': [None, 4, 5, None], ... 'animals': ["Flamingo", "Horse", None, "Centipede"]}) >>> table = pa.Table.from_pandas(df) >>> for i in table.itercolumns(): ... print(i.null_count) ... 2 1
- join(self, right_table, keys, right_keys=None, join_type='left outer', left_suffix=None, right_suffix=None, coalesce_keys=True, use_threads=True)#
Perform a join between this table and another one.
Result of the join will be a new Table, where further operations can be applied.
- Parameters
- right_table
Table
The table to join to the current one, acting as the right table in the join operation.
- keys
str
orlist
[str
] The columns from current table that should be used as keys of the join operation left side.
- right_keys
str
orlist
[str
], defaultNone
The columns from the right_table that should be used as keys on the join operation right side. When
None
use the same key names as the left table.- join_type
str
, default “left outer” The kind of join that should be performed, one of (“left semi”, “right semi”, “left anti”, “right anti”, “inner”, “left outer”, “right outer”, “full outer”)
- left_suffix
str
, defaultNone
Which suffix to add to right column names. This prevents confusion when the columns in left and right tables have colliding names.
- right_suffix
str
, defaultNone
Which suffic to add to the left column names. This prevents confusion when the columns in left and right tables have colliding names.
- coalesce_keysbool, default
True
If the duplicated keys should be omitted from one of the sides in the join result.
- use_threadsbool, default
True
Whenever to use multithreading or not.
- right_table
- Returns
Examples
>>> import pandas as pd >>> import pyarrow as pa >>> df1 = pd.DataFrame({'id': [1, 2, 3], ... 'year': [2020, 2022, 2019]}) >>> df2 = pd.DataFrame({'id': [3, 4], ... 'n_legs': [5, 100], ... 'animal': ["Brittle stars", "Centipede"]}) >>> t1 = pa.Table.from_pandas(df1) >>> t2 = pa.Table.from_pandas(df2)
Left outer join:
>>> t1.join(t2, 'id') pyarrow.Table id: int64 year: int64 n_legs: int64 animal: string ---- id: [[3,1,2]] year: [[2019,2020,2022]] n_legs: [[5,null,null]] animal: [["Brittle stars",null,null]]
Full outer join:
>>> t1.join(t2, 'id', join_type="full outer") pyarrow.Table id: int64 year: int64 n_legs: int64 animal: string ---- id: [[3,1,2],[4]] year: [[2019,2020,2022],[null]] n_legs: [[5,null,null],[100]] animal: [["Brittle stars",null,null],["Centipede"]]
Right outer join:
>>> t1.join(t2, 'id', join_type="right outer") pyarrow.Table year: int64 id: int64 n_legs: int64 animal: string ---- year: [[2019],[null]] id: [[3],[4]] n_legs: [[5],[100]] animal: [["Brittle stars"],["Centipede"]]
Right anti join
>>> t1.join(t2, 'id', join_type="right anti") pyarrow.Table id: int64 n_legs: int64 animal: string ---- id: [[4]] n_legs: [[100]] animal: [["Centipede"]]
- nbytes#
Total number of bytes consumed by the elements of the table.
In other words, the sum of bytes from all buffer ranges referenced.
Unlike get_total_buffer_size this method will account for array offsets.
If buffers are shared between arrays then the shared portion will only be counted multiple times.
The dictionary of dictionary arrays will always be counted in their entirety even if the array only references a portion of the dictionary.
Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'n_legs': [None, 4, 5, None], ... 'animals': ["Flamingo", "Horse", None, "Centipede"]}) >>> table = pa.Table.from_pandas(df) >>> table.nbytes 72
- num_columns#
Number of columns in this table.
- Returns
Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'n_legs': [None, 4, 5, None], ... 'animals': ["Flamingo", "Horse", None, "Centipede"]}) >>> table = pa.Table.from_pandas(df) >>> table.num_columns 2
- num_rows#
Number of rows in this table.
Due to the definition of a table, all columns have the same number of rows.
- Returns
Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'n_legs': [None, 4, 5, None], ... 'animals': ["Flamingo", "Horse", None, "Centipede"]}) >>> table = pa.Table.from_pandas(df) >>> table.num_rows 4
- remove_column(self, int i)#
Create new Table with the indicated column removed.
Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'n_legs': [2, 4, 5, 100], ... 'animals': ["Flamingo", "Horse", "Brittle stars", "Centipede"]}) >>> table = pa.Table.from_pandas(df) >>> table.remove_column(1) pyarrow.Table n_legs: int64 ---- n_legs: [[2,4,5,100]]
- rename_columns(self, names)#
Create new table with columns renamed to provided names.
Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'n_legs': [2, 4, 5, 100], ... 'animals': ["Flamingo", "Horse", "Brittle stars", "Centipede"]}) >>> table = pa.Table.from_pandas(df) >>> new_names = ["n", "name"] >>> table.rename_columns(new_names) pyarrow.Table n: int64 name: string ---- n: [[2,4,5,100]] name: [["Flamingo","Horse","Brittle stars","Centipede"]]
- replace_schema_metadata(self, metadata=None)#
Create shallow copy of table by replacing schema key-value metadata with the indicated new metadata (which may be None), which deletes any existing metadata.
Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'year': [2020, 2022, 2019, 2021], ... 'n_legs': [2, 4, 5, 100], ... 'animals': ["Flamingo", "Horse", "Brittle stars", "Centipede"]}) >>> table = pa.Table.from_pandas(df)
Constructing a Table with pyarrow schema and metadata:
>>> my_schema = pa.schema([ ... pa.field('n_legs', pa.int64()), ... pa.field('animals', pa.string())], ... metadata={"n_legs": "Number of legs per animal"}) >>> table= pa.table(df, my_schema) >>> table.schema n_legs: int64 animals: string -- schema metadata -- n_legs: 'Number of legs per animal' pandas: ...
Create a shallow copy of a Table with deleted schema metadata:
>>> table.replace_schema_metadata().schema n_legs: int64 animals: string
Create a shallow copy of a Table with new schema metadata:
>>> metadata={"animals": "Which animal"} >>> table.replace_schema_metadata(metadata = metadata).schema n_legs: int64 animals: string -- schema metadata -- animals: 'Which animal'
- schema#
Schema of the table and its columns.
- Returns
Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'n_legs': [2, 4, 5, 100], ... 'animals': ["Flamingo", "Horse", "Brittle stars", "Centipede"]}) >>> table = pa.Table.from_pandas(df) >>> table.schema n_legs: int64 animals: string -- schema metadata -- pandas: '{"index_columns": [{"kind": "range", "name": null, "start": 0, "' ...
- select(self, columns)#
Select columns of the Table.
Returns a new Table with the specified columns, and metadata preserved.
- Parameters
- columnslist-like
The column names or integer indices to select.
- Returns
Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'year': [2020, 2022, 2019, 2021], ... 'n_legs': [2, 4, 5, 100], ... 'animals': ["Flamingo", "Horse", "Brittle stars", "Centipede"]}) >>> table = pa.Table.from_pandas(df) >>> table.select([0,1]) pyarrow.Table year: int64 n_legs: int64 ---- year: [[2020,2022,2019,2021]] n_legs: [[2,4,5,100]] >>> table.select(["year"]) pyarrow.Table year: int64 ---- year: [[2020,2022,2019,2021]]
- set_column(self, int i, field_, column)#
Replace column in Table at position.
- Parameters
- Returns
Table
New table with the passed column set.
Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'n_legs': [2, 4, 5, 100], ... 'animals': ["Flamingo", "Horse", "Brittle stars", "Centipede"]}) >>> table = pa.Table.from_pandas(df)
Replace a column:
>>> year = [2021, 2022, 2019, 2021] >>> table.set_column(1,'year', [year]) pyarrow.Table n_legs: int64 year: int64 ---- n_legs: [[2,4,5,100]] year: [[2021,2022,2019,2021]]
- shape#
Dimensions of the table: (#rows, #columns).
Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'n_legs': [None, 4, 5, None], ... 'animals': ["Flamingo", "Horse", None, "Centipede"]}) >>> table = pa.Table.from_pandas(df) >>> table.shape (4, 2)
- slice(self, offset=0, length=None)#
Compute zero-copy slice of this Table.
- Parameters
- Returns
Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'year': [2020, 2022, 2019, 2021], ... 'n_legs': [2, 4, 5, 100], ... 'animals': ["Flamingo", "Horse", "Brittle stars", "Centipede"]}) >>> table = pa.Table.from_pandas(df) >>> table.slice(length=3) pyarrow.Table year: int64 n_legs: int64 animals: string ---- year: [[2020,2022,2019]] n_legs: [[2,4,5]] animals: [["Flamingo","Horse","Brittle stars"]] >>> table.slice(offset=2) pyarrow.Table year: int64 n_legs: int64 animals: string ---- year: [[2019,2021]] n_legs: [[5,100]] animals: [["Brittle stars","Centipede"]] >>> table.slice(offset=2, length=1) pyarrow.Table year: int64 n_legs: int64 animals: string ---- year: [[2019]] n_legs: [[5]] animals: [["Brittle stars"]]
- sort_by(self, sorting)#
Sort the table by one or multiple columns.
- Parameters
- Returns
Table
A new table sorted according to the sort keys.
Examples
>>> import pandas as pd >>> import pyarrow as pa >>> df = pd.DataFrame({'year': [2020, 2022, 2021, 2022, 2019, 2021], ... 'n_legs': [2, 2, 4, 4, 5, 100], ... 'animal': ["Flamingo", "Parrot", "Dog", "Horse", ... "Brittle stars", "Centipede"]}) >>> table = pa.Table.from_pandas(df) >>> table.sort_by('animal') pyarrow.Table year: int64 n_legs: int64 animal: string ---- year: [[2019,2021,2021,2020,2022,2022]] n_legs: [[5,100,4,2,4,2]] animal: [["Brittle stars","Centipede","Dog","Flamingo","Horse","Parrot"]]
- take(self, indices)#
Select rows from the table.
See
pyarrow.compute.take()
for full usage.- Parameters
- indices
Array
orarray-like
The indices in the table whose rows will be returned.
- indices
- Returns
- taken
Table
A table with the same schema, containing the taken rows.
- taken
Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'year': [2020, 2022, 2019, 2021], ... 'n_legs': [2, 4, 5, 100], ... 'animals': ["Flamingo", "Horse", "Brittle stars", "Centipede"]}) >>> table = pa.Table.from_pandas(df) >>> table.take([1,3]) pyarrow.Table year: int64 n_legs: int64 animals: string ---- year: [[2022,2021]] n_legs: [[4,100]] animals: [["Horse","Centipede"]]
- to_batches(self, max_chunksize=None)#
Convert Table to a list of RecordBatch objects.
Note that this method is zero-copy, it merely exposes the same data under a different API.
- Parameters
- Returns
Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'n_legs': [2, 4, 5, 100], ... 'animals': ["Flamingo", "Horse", "Brittle stars", "Centipede"]}) >>> table = pa.Table.from_pandas(df)
Convert a Table to a RecordBatch:
>>> table.to_batches()[0].to_pandas() n_legs animals 0 2 Flamingo 1 4 Horse 2 5 Brittle stars 3 100 Centipede
Convert a Table to a list of RecordBatches:
>>> table.to_batches(max_chunksize=2)[0].to_pandas() n_legs animals 0 2 Flamingo 1 4 Horse >>> table.to_batches(max_chunksize=2)[1].to_pandas() n_legs animals 0 5 Brittle stars 1 100 Centipede
- to_pandas(self, memory_pool=None, categories=None, bool strings_to_categorical=False, bool zero_copy_only=False, bool integer_object_nulls=False, bool date_as_object=True, bool timestamp_as_object=False, bool use_threads=True, bool deduplicate_objects=True, bool ignore_metadata=False, bool safe=True, bool split_blocks=False, bool self_destruct=False, types_mapper=None)#
Convert to a pandas-compatible NumPy array or DataFrame, as appropriate
- Parameters
- memory_pool
MemoryPool
, defaultNone
Arrow MemoryPool to use for allocations. Uses the default memory pool is not passed.
- strings_to_categoricalbool, default
False
Encode string (UTF8) and binary types to pandas.Categorical.
- categories
list
, defaultempty
List of fields that should be returned as pandas.Categorical. Only applies to table-like data structures.
- zero_copy_onlybool, default
False
Raise an ArrowException if this function call would require copying the underlying data.
- integer_object_nullsbool, default
False
Cast integers with nulls to objects
- date_as_objectbool, default
True
Cast dates to objects. If False, convert to datetime64[ns] dtype.
- timestamp_as_objectbool, default
False
Cast non-nanosecond timestamps (np.datetime64) to objects. This is useful if you have timestamps that don’t fit in the normal date range of nanosecond timestamps (1678 CE-2262 CE). If False, all timestamps are converted to datetime64[ns] dtype.
- use_threadsbool, default
True
Whether to parallelize the conversion using multiple threads.
- deduplicate_objectsbool, default
False
Do not create multiple copies Python objects when created, to save on memory use. Conversion will be slower.
- ignore_metadatabool, default
False
If True, do not use the ‘pandas’ metadata to reconstruct the DataFrame index, if present
- safebool, default
True
For certain data types, a cast is needed in order to store the data in a pandas DataFrame or Series (e.g. timestamps are always stored as nanoseconds in pandas). This option controls whether it is a safe cast or not.
- split_blocksbool, default
False
If True, generate one internal “block” for each column when creating a pandas.DataFrame from a RecordBatch or Table. While this can temporarily reduce memory note that various pandas operations can trigger “consolidation” which may balloon memory use.
- self_destructbool, default
False
EXPERIMENTAL: If True, attempt to deallocate the originating Arrow memory while converting the Arrow object to pandas. If you use the object after calling to_pandas with this option it will crash your program.
Note that you may not see always memory usage improvements. For example, if multiple columns share an underlying allocation, memory can’t be freed until all columns are converted.
- types_mapperfunction, default
None
A function mapping a pyarrow DataType to a pandas ExtensionDtype. This can be used to override the default pandas type for conversion of built-in pyarrow types or in absence of pandas_metadata in the Table schema. The function receives a pyarrow DataType and is expected to return a pandas ExtensionDtype or
None
if the default conversion should be used for that type. If you have a dictionary mapping, you can passdict.get
as function.
- memory_pool
- Returns
pandas.Series
orpandas.DataFrame
depending ontype
of object
Examples
>>> import pyarrow as pa >>> import pandas as pd
Convert a Table to pandas DataFrame:
>>> table = pa.table([ ... pa.array([2, 4, 5, 100]), ... pa.array(["Flamingo", "Horse", "Brittle stars", "Centipede"]) ... ], names=['n_legs', 'animals']) >>> table.to_pandas() n_legs animals 0 2 Flamingo 1 4 Horse 2 5 Brittle stars 3 100 Centipede >>> isinstance(table.to_pandas(), pd.DataFrame) True
Convert a RecordBatch to pandas DataFrame:
>>> import pyarrow as pa >>> n_legs = pa.array([2, 4, 5, 100]) >>> animals = pa.array(["Flamingo", "Horse", "Brittle stars", "Centipede"]) >>> batch = pa.record_batch([n_legs, animals], ... names=["n_legs", "animals"]) >>> batch pyarrow.RecordBatch n_legs: int64 animals: string >>> batch.to_pandas() n_legs animals 0 2 Flamingo 1 4 Horse 2 5 Brittle stars 3 100 Centipede >>> isinstance(batch.to_pandas(), pd.DataFrame) True
Convert a Chunked Array to pandas Series:
>>> import pyarrow as pa >>> n_legs = pa.chunked_array([[2, 2, 4], [4, 5, 100]]) >>> n_legs.to_pandas() 0 2 1 2 2 4 3 4 4 5 5 100 dtype: int64 >>> isinstance(n_legs.to_pandas(), pd.Series) True
- to_pydict(self)#
Convert the Table to a dict or OrderedDict.
- Returns
Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'n_legs': [2, 4, 5, 100], ... 'animals': ["Flamingo", "Horse", "Brittle stars", "Centipede"]}) >>> table = pa.Table.from_pandas(df) >>> table.to_pydict() {'n_legs': [2, 4, 5, 100], 'animals': ['Flamingo', 'Horse', 'Brittle stars', 'Centipede']}
- to_pylist(self)#
Convert the Table to a list of rows / dictionaries.
- Returns
Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'n_legs': [2, 4, 5, 100], ... 'animals': ["Flamingo", "Horse", "Brittle stars", "Centipede"]}) >>> table = pa.Table.from_pandas(df) >>> table.to_pylist() [{'n_legs': 2, 'animals': 'Flamingo'}, {'n_legs': 4, 'animals': 'Horse'}, ...
- to_reader(self, max_chunksize=None)#
Convert the Table to a RecordBatchReader.
Note that this method is zero-copy, it merely exposes the same data under a different API.
- Parameters
- Returns
- RecordBatchReader
Examples
>>> import pyarrow as pa >>> import pandas as pd >>> df = pd.DataFrame({'n_legs': [2, 4, 5, 100], ... 'animals': ["Flamingo", "Horse", "Brittle stars", "Centipede"]}) >>> table = pa.Table.from_pandas(df)
Convert a Table to a RecordBatchReader:
>>> table.to_reader() <pyarrow.lib.RecordBatchReader object at ...>
>>> reader = table.to_reader() >>> reader.schema n_legs: int64 animals: string -- schema metadata -- pandas: '{"index_columns": [{"kind": "range", "name": null, "start": 0, "' + 509 >>> reader.read_all() pyarrow.Table n_legs: int64 animals: string ---- n_legs: [[2,4,5,100]] animals: [["Flamingo","Horse","Brittle stars","Centipede"]]
- to_string(self, *, show_metadata=False, preview_cols=0)#
Return human-readable string representation of Table.
- unify_dictionaries(self, MemoryPool memory_pool=None)#
Unify dictionaries across all chunks.
This method returns an equivalent table, but where all chunks of each column share the same dictionary values. Dictionary indices are transposed accordingly.
Columns without dictionaries are returned unchanged.
- Parameters
- memory_pool
MemoryPool
, defaultNone
For memory allocations, if required, otherwise use default pool
- memory_pool
- Returns
Examples
>>> import pyarrow as pa >>> arr_1 = pa.array(["Flamingo", "Parot", "Dog"]).dictionary_encode() >>> arr_2 = pa.array(["Horse", "Brittle stars", "Centipede"]).dictionary_encode() >>> c_arr = pa.chunked_array([arr_1, arr_2]) >>> table = pa.table([c_arr], names=["animals"]) >>> table pyarrow.Table animals: dictionary<values=string, indices=int32, ordered=0> ---- animals: [ -- dictionary: ["Flamingo","Parot","Dog"] -- indices: [0,1,2], -- dictionary: ["Horse","Brittle stars","Centipede"] -- indices: [0,1,2]]
Unify dictionaries across both chunks:
>>> table.unify_dictionaries() pyarrow.Table animals: dictionary<values=string, indices=int32, ordered=0> ---- animals: [ -- dictionary: ["Flamingo","Parot","Dog","Horse","Brittle stars","Centipede"] -- indices: [0,1,2], -- dictionary: ["Flamingo","Parot","Dog","Horse","Brittle stars","Centipede"] -- indices: [3,4,5]]
- validate(self, *, full=False)#
Perform validation checks. An exception is raised if validation fails.
By default only cheap validation checks are run. Pass full=True for thorough validation checks (potentially O(n)).