New submission from Jáchym Barvínek:
An identity function is sometimes useful in functional-style programming as a
dummy or default value.
For example, we can sometimes see a pattern like this (e.g. in
itertools.groupby):
def f(params, key=None):
if key is None:
key = lambda x: x
...
However, if we had a canonical itentity function:
def identity(x):
return x
we could instead write:
def f(params, key=identity):
...
and the intended use of the function f and it's functioning would be more
obvious simply from it's signature, while also saving a little code.
As zen of Python says: Explicit is better than implicit.
Of course, we can now write:
def f(params, key=lambda x: x):
...
but the reason why is not used is probably that it feels a bit awkward to more
people than just me.
----------
components: Library (Lib)
messages: 273643
nosy: Jáchym Barvínek
priority: normal
severity: normal
status: open
title: Add identity function to functools
type: enhancement
versions: Python 3.6
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Python tracker <[email protected]>
<https://bugs.python.org/issue27858>
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