STYLE place standard library imports at top of file

[MarcoGorelli]

Imports should typically be placed at the top of files. Sometimes, imports are placed inside functions to:

• avoid circular imports
• avoid ImportError if it's an optional dependency

Standard library imports should really always be at the top of files.

Noticed in #49645 that this is often not the case

I've made a script to automate detecting when this is the case. So the task is:

git checkout -b standard-library-imports main
git pull [email protected]:MarcoGorelli/pandas.git standard-library-imports
git reset --hard FETCH_HEAD
pre-commit run stdlib-imports --all-files

Then, fixup any errors that are reported. Finally, stage your changes, commit them, push them to your fork, and open a pull request

Feel free to reach out if you into any issues along the way

If any wants to take this, it would be a nice and welcome clean up!

---

EDIT: after going through a PR, I'm not sure it's worth introducing a check for this - but we can still take some of the cleanups it found

[mroeschke]

Noting in the past that some stdlib imports were deferred (i.e. not at the top level) to help import time (not sure if this is still the case)

pandas/pandas/io/common.py

Lines 259 to 266 in e41b6d7

	def urlopen(*args, **kwargs):
	"""
	Lazy-import wrapper for stdlib urlopen, as that imports a big chunk of
	the stdlib.
	"""
	import urllib.request
	return urllib.request.urlopen(*args, **kwargs)

[MarcoGorelli]

Ah thanks! Can probably just respect the blocklist

pandas/ci/code_checks.sh

Lines 48 to 50 in bcb8346

	blocklist = {'bs4', 'gcsfs', 'html5lib', 'http', 'ipython', 'jinja2', 'hypothesis',
	'lxml', 'matplotlib', 'openpyxl', 'py', 'pytest', 's3fs', 'scipy',
	'tables', 'urllib.request', 'xlrd', 'xlsxwriter'}

EDIT: done

[grtcoder]

Hey, I would like to work on this.

[MarcoGorelli]

sure go ahead

[zemnly]

Hi, can I take this ?

[MarcoGorelli]

looks like @grtcoder is already working on it

[natmokval]

Hi @grtcoder. Do you mind if I will work on this issue as well?

[MarcoGorelli]

feel free to go ahead, doesn't look like it's being worked on

[Thextan]

@natmokval I am starting on this one. I will start with the files under pandas/core/ and pandas/io

[Thextan]

Finished all files except pandas/tests/*. I will work on those next.

[seanjedi]

Is there anything for this issue that I can work on?

[Thextan]

Sean, I have just about finished this one. I am working on the last 3 files now. Sent with [Proton Mail](https://proton.me/) secure email.

…

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[seanjedi]

Alright, thanks for letting me know!