pyarrow.dataset.Expression#

class pyarrow.dataset.Expression#

Bases: pyarrow.lib._Weakrefable

A logical expression to be evaluated against some input.

To create an expression:

  • Use the factory function pyarrow.compute.scalar() to create a scalar (not necessary when combined, see example below).

  • Use the factory function pyarrow.compute.field() to reference a field (column in table).

  • Compare fields and scalars with <, <=, ==, >=, >.

  • Combine expressions using python operators & (logical and), | (logical or) and ~ (logical not). Note: python keywords and, or and not cannot be used to combine expressions.

  • Create expression predicates using Expression methods such as pyarrow.compute.Expression.isin().

Examples

>>> import pyarrow.compute as pc
>>> (pc.field("a") < pc.scalar(3)) | (pc.field("b") > 7)
<pyarrow.compute.Expression ((a < 3:int64) or (b > 7:int64))>
>>> ds.field('a') != 3
<pyarrow.compute.Expression (a != 3)>
>>> ds.field('a').isin([1, 2, 3])
<pyarrow.compute.Expression (a is in [
  1,
  2,
  3
])>
__init__(*args, **kwargs)#

Methods

__init__(*args, **kwargs)

cast(self, type, bool safe=True)

Explicitly set or change the expression's data type.

equals(self, Expression other)

is_null(self, bool nan_is_null=False)

Check whether the expression is null.

is_valid(self)

Check whether the expression is not-null (valid).

isin(self, values)

Check whether the expression is contained in values.
cast(self, type, bool safe=True)#

Explicitly set or change the expression’s data type.

This creates a new expression equivalent to calling the cast compute function on this expression.

Parameters
typeDataType

Type to cast array to.

safebool, default True

Whether to check for conversion errors such as overflow.

Returns
castExpression
equals(self, Expression other)#
is_null(self, bool nan_is_null=False)#

Check whether the expression is null.

This creates a new expression equivalent to calling the is_null compute function on this expression.

Parameters
nan_is_nullbool, default False

Whether floating-point NaNs are considered null.

Returns
is_nullExpression
is_valid(self)#

Check whether the expression is not-null (valid).

This creates a new expression equivalent to calling the is_valid compute function on this expression.

Returns
is_validExpression
isin(self, values)#

Check whether the expression is contained in values.

This creates a new expression equivalent to calling the is_in compute function on this expression.

Parameters
valuesArray or iterable

The values to check for.

Returns
isinExpression

A new expression that, when evaluated, checks whether this expression’s value is contained in values.

previous

pyarrow.dataset.Scanner

next

pyarrow.dataset.InMemoryDataset