gh-118761: Improve import time of pprint

[hugovk]

Improves import time by up to seven times. Measured with a PGO and LTO non-debug build on macOS.

• The slowest import in pprint is dataclasses (taking 0.0012s / 55.2% of import time), and used in only two functions.

• After deferring dataclasses, the next is re (0.005s / 30.1% of the new import time), only used in one function.

• After deferring re, the next are collections (0.002s / 14.8%) and types (0.000s / 2.4%). I left these, as their times are low and they're less straightforward to defer.

-X importtime

Running: pip install tuna && ./python.exe -X importtime -c 'import pprint' 2> import.log && tuna import.log

total import time: 0.022s -> 0.011s = x2 as fast

main	PR

pprint import time: 0.014s -> 0.002s = x7 as fast

main	PR

hyperfine: 19.2 ms -> 10.4 ms = x1.8 as fast

main

❯ hyperfine --warmup 8 "./python.exe -c 'import pprint'"
Benchmark 1: ./python.exe -c 'import pprint'
  Time (mean ± σ):      19.2 ms ±   0.7 ms    [User: 15.8 ms, System: 2.8 ms]
  Range (min … max):    18.1 ms …  21.3 ms    135 runs

PR

❯ hyperfine --warmup 8 "./python.exe -c 'import pprint'"
Benchmark 1: ./python.exe -c 'import pprint'
  Time (mean ± σ):      10.4 ms ±   0.4 ms    [User: 8.1 ms, System: 1.8 ms]
  Range (min … max):     9.8 ms …  12.4 ms    212 runs

Also add some PEP 8 whitespace to remove some distracting IDE warnings.

• Issue: Improve import time of various stdlib modules #118761

[hugovk]

By the way, what's the reason for importing with underscores?

import collections as _collections
import sys as _sys
import types as _types
from io import StringIO as _StringIO

[AA-Turner]

Looks fine -- I wouldn't change the whitespace personally but up to you.

collections you could do by hardcoding the repr and adding a test that they're the same? I agree probably not worth it, though.

A