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In Doc/library/re.rst rename a variable from match to m #123003

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In Doc/library/re.rst rename a variable from match to m #123003

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In Doc/library/re.rst rename a variable from `match` to `m`
JohnADawson Aug 14, 2024
c130999
Merge branch 'main' into doc-re-match
StanFromIreland Sep 5, 2025
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6 changes: 3 additions & 3 deletions Doc/library/re.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -1357,9 +1357,9 @@ Since :meth:`~Pattern.match` and :meth:`~Pattern.search` return ``None``
when there is no match, you can test whether there was a match with a simple
``if`` statement::
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Suggested change
``if`` statement::
``if ... is not None`` statement::

I agree with Adam that the example should be updated, but the text should be updated accordingly.


match = re.search(pattern, string)
if match:
process(match)
m = re.search(pattern, string)
if m:
process(m)
Comment on lines +1379 to +1381
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To promote good practice, we could suggest

Suggested change
m = re.search(pattern, string)
if m:
process(m)
m = re.search(pattern, string)
if m is not None:
process(m)

If we want to suggest using assignment expressions, we could also use:

Suggested change
m = re.search(pattern, string)
if m:
process(m)
if m := re.search(pattern, string):
process(m)

Or both! (I probably wouldn't go for this...)

Suggested change
m = re.search(pattern, string)
if m:
process(m)
if (m := re.search(pattern, string)) is not None:
process(m)

A

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Having is not None does not seem to me better practice. There are two possibly relevant parts of PEP 8:

Also, beware of writing if x when you really mean if x is not None – e.g. when testing whether a variable or argument that defaults to None was set to some other value. The other value might have a type (such as a container) that could be false in a boolean context!

and

For sequences, (strings, lists, tuples), use the fact that empty sequences are false:

# Correct:
if not seq:
if seq:
# Wrong:
if len(seq):
if not len(seq):

Now, the first does not apply here, because, as the documentation immediately before the example says,

Match objects always have a boolean value of True. Since match() and search() return None when there is no match, you can test whether there was a match with a simple if statement [Emphasis added]

On the other hand, the spirit of the second excerpt from PEP 8 argues for availing of truthiness and falsiness and thus against the redundant is not None.

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I do not have a strong opinion on whether to use the assignment operator here. (I myself would not, reserving it for cases like

[process(m) for pattern in patterns if (m := re.search(pattern, string)]

and

if ...:
    ...
elif (m := re.search(pattern, string):
    process(m)

).


.. class:: Match

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