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

[JohnADawson]

Since version 3.10 match has been a soft keyword, so examples ought to not use
it as a variable name.

https://docs.python.org/3/reference/lexical_analysis.html#soft-keywords

The new name is m, that used for match objects in the other examples in
re.rst.

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📚 Documentation preview 📚: https://cpython-previews--123003.org.readthedocs.build/

[ghost]

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[picnixz]

I would say it's also for consistency with the rest of the module where we use m = (...).match.

Nevermind, you already observed it.

[AA-Turner]

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

[JohnADawson]

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.

[JohnADawson]

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)

).

[StanFromIreland]

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.