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Chooses eval engine automatically depending on whether numexpr is installed #12605

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Chooses eval engine automatically depending on whether numexpr is installed #12605

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ec6a25b
Automatically chooses eval engine based on whether numexpr is installed
robintw Mar 13, 2016
8805538
Fixed linter error
robintw Mar 13, 2016
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13 changes: 11 additions & 2 deletions pandas/computation/eval.py
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Original file line number Diff line number Diff line change
Expand Up @@ -131,7 +131,7 @@ def _check_for_locals(expr, stack_level, parser):
raise SyntaxError(msg)


def eval(expr, parser='pandas', engine='numexpr', truediv=True,
def eval(expr, parser='pandas', engine=None, truediv=True,
local_dict=None, global_dict=None, resolvers=(), level=0,
target=None, inplace=None):
"""Evaluate a Python expression as a string using various backends.
Expand Down Expand Up @@ -160,7 +160,7 @@ def eval(expr, parser='pandas', engine='numexpr', truediv=True,
``'python'`` parser to retain strict Python semantics. See the
:ref:`enhancing performance <enhancingperf.eval>` documentation for
more details.
engine : string, default 'numexpr', {'python', 'numexpr'}
engine : string, default None, {'python', 'numexpr'}

The engine used to evaluate the expression. Supported engines are

Expand All @@ -172,6 +172,9 @@ def eval(expr, parser='pandas', engine='numexpr', truediv=True,

More backends may be available in the future.

If set to None (the default) then uses ``'numexpr'`` if available,
otherwise uses ``'python'``.

truediv : bool, optional
Whether to use true division, like in Python >= 3
local_dict : dict or None, optional
Expand Down Expand Up @@ -227,6 +230,12 @@ def eval(expr, parser='pandas', engine='numexpr', truediv=True,
raise ValueError("multi-line expressions are only valid in the "
"context of data, use DataFrame.eval")

if engine is None:
if _NUMEXPR_INSTALLED:
engine = 'numexpr'
else:
engine = 'python'

first_expr = True
for expr in exprs:
expr = _convert_expression(expr)
Expand Down