[Python-Dev] PEP 563: Postponed Evaluation of Annotations

[Barry Warsaw]

On Nov 2, 2017, at 23:22, Nick Coghlan <ncoghlan at gmail.com> wrote:
> Another point worth noting is that merely importing the typing module
> is expensive:
> 
> $ python -m perf timeit -s "from importlib import reload; import
> typing" "reload(typing)"
> .....................
> Mean +- std dev: 10.6 ms +- 0.6 ms
> 
> 10 ms is a *big* chunk out of a CLI application's startup time budget.

Far and away so, except for the re module.

% ./python.exe -X importtime -c "import typing"
import time: self [us] | cumulative | imported package
import time:        72 |         72 |     _codecs
import time:       625 |        696 |   codecs
import time:       354 |        354 |   encodings.aliases
import time:       713 |       1762 | encodings
import time:       198 |        198 | encodings.utf_8
import time:        98 |         98 | _signal
import time:       233 |        233 | encodings.latin_1
import time:       353 |        353 |     _weakrefset
import time:       264 |        617 |   abc
import time:       402 |       1018 | io
import time:       136 |        136 |       _stat
import time:       197 |        333 |     stat
import time:       227 |        227 |       genericpath
import time:       377 |        604 |     posixpath
import time:      2812 |       2812 |     _collections_abc
import time:       787 |       4534 |   os
import time:       315 |        315 |   _sitebuiltins
import time:       336 |        336 |   sitecustomize
import time:       114 |        114 |   usercustomize
import time:      1064 |       6361 | site
import time:       160 |        160 |       _operator
import time:      1412 |       1571 |     operator
import time:       371 |        371 |     keyword
import time:       817 |        817 |       _heapq
import time:       762 |       1579 |     heapq
import time:       272 |        272 |     itertools
import time:       635 |        635 |     reprlib
import time:        99 |         99 |     _collections
import time:      3580 |       8104 |   collections
import time:       112 |        112 |       _functools
import time:       781 |        892 |     functools
import time:      1774 |       2666 |   contextlib
import time:       272 |        272 |       types
import time:       861 |       1132 |     enum
import time:        76 |         76 |       _sre
import time:       426 |        426 |         sre_constants
import time:       446 |        872 |       sre_parse
import time:       414 |       1361 |     sre_compile
import time:        79 |         79 |     _locale
import time:       190 |        190 |     copyreg
import time:     17200 |      19961 |   re
import time:       374 |        374 |   collections.abc
import time:     15124 |      46226 | typing

-Barry

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