Import platform later

[pjonsson]

It takes a while to import
platform, so use sys.platform
to check for macOS/Linux, and
only import platform to detect
BSD dialects.

Tested inside a python:3.10-bookworm container with a test.py containing:

import typer.main

and then python3 test.py followed by:

python3 -X importtime test.py > timing.txt 2>&1

a couple of times. Times fluctuate a bit, but here's a reasonable before:

import time: self [us] | cumulative | imported package
import time:        91 |         91 |   _io
import time:        17 |         17 |   marshal
import time:       178 |        178 |   posix
import time:       353 |        638 | _frozen_importlib_external
import time:        59 |         59 |   time
import time:        94 |        152 | zipimport
import time:        25 |         25 |     _codecs
import time:       266 |        291 |   codecs
import time:       232 |        232 |   encodings.aliases
import time:       345 |        867 | encodings
import time:       154 |        154 | encodings.utf_8
import time:        50 |         50 | _signal
import time:        20 |         20 |     _abc
import time:       125 |        144 |   abc
import time:       165 |        309 | io
import time:        25 |         25 |       _stat
import time:        91 |        116 |     stat
import time:       511 |        511 |     _collections_abc
import time:        79 |         79 |       genericpath
import time:       112 |        190 |     posixpath
import time:       439 |       1255 |   os
import time:       120 |        120 |   _sitebuiltins
import time:       279 |        279 |   _distutils_hack
import time:        41 |         41 |   sitecustomize
import time:        28 |         28 |   usercustomize
import time:       466 |       2186 | site
import time:       165 |        165 |             types
import time:       346 |        510 |           enum
import time:        38 |         38 |             _sre
import time:       486 |        486 |               sre_constants
import time:       182 |        668 |             sre_parse
import time:       154 |        859 |           sre_compile
import time:        54 |         54 |               itertools
import time:        68 |         68 |               keyword
import time:        37 |         37 |                 _operator
import time:       129 |        165 |               operator
import time:        83 |         83 |               reprlib
import time:        62 |         62 |               _collections
import time:       424 |        854 |             collections
import time:        28 |         28 |             _functools
import time:       279 |       1160 |           functools
import time:        35 |         35 |           _locale
import time:       128 |        128 |           copyreg
import time:       301 |       2991 |         re
import time:        86 |       3076 |       fnmatch
import time:        45 |         45 |       errno
import time:       197 |        197 |       zlib
import time:       171 |        171 |         _compression
import time:       131 |        131 |         _bz2
import time:       170 |        470 |       bz2
import time:       234 |        234 |         _lzma
import time:       174 |        407 |       lzma
import time:       347 |       4541 |     shutil
import time:        83 |         83 |         __future__
import time:        85 |         85 |           collections.abc
import time:       478 |        478 |               _ast
import time:       447 |        447 |               contextlib
import time:       498 |       1422 |             ast
import time:        84 |         84 |                 _opcode
import time:       134 |        217 |               opcode
import time:       311 |        528 |             dis
import time:       125 |        125 |                 warnings
import time:       104 |        229 |               importlib
import time:        98 |        327 |             importlib.machinery
import time:        94 |         94 |                 token
import time:       509 |        602 |               tokenize
import time:        78 |        679 |             linecache
import time:       778 |       3731 |           inspect
import time:      1042 |       1042 |           typing
import time:       578 |        578 |           gettext
import time:       130 |        130 |               math
import time:       144 |        144 |               _datetime
import time:       432 |        706 |             datetime
import time:       152 |        152 |                 _weakrefset
import time:       236 |        388 |               weakref
import time:       250 |        637 |             click._compat
import time:       463 |        463 |                 threading
import time:        80 |        543 |               click.globals
import time:       178 |        178 |               click.utils
import time:       216 |        936 |             click.exceptions
import time:       771 |       3049 |           click.types
import time:       149 |        149 |           click._utils
import time:       191 |        191 |             click.parser
import time:       110 |        301 |           click.formatting
import time:       136 |        136 |           click.termui
import time:       620 |       9686 |         click.core
import time:       154 |        154 |         click.decorators
import time:       173 |      10095 |       click
import time:        10 |      10105 |     click.exceptions
import time:        85 |         85 |     typer.colors
import time:       383 |        383 |           signal
import time:       111 |        111 |           fcntl
import time:        39 |         39 |           msvcrt
import time:        87 |         87 |           _posixsubprocess
import time:        85 |         85 |           select
import time:       321 |        321 |           selectors
import time:       336 |       1360 |         subprocess
import time:      1255 |       2615 |       platform
import time:       213 |        213 |       traceback
import time:        44 |         44 |           _winapi
import time:        33 |         33 |           nt
import time:        28 |         28 |           nt
import time:        27 |         27 |           nt
import time:        28 |         28 |           nt
import time:       238 |        395 |         ntpath
import time:        70 |         70 |           urllib
import time:       686 |        686 |           ipaddress
import time:       604 |       1359 |         urllib.parse
import time:       408 |       2161 |       pathlib
import time:       156 |        156 |         _uuid
import time:       254 |        409 |       uuid
import time:       122 |        122 |       typer._types
import time:       171 |        171 |       typer._typing
import time:        84 |         84 |             importlib._abc
import time:       166 |        250 |           importlib.util
import time:       176 |        176 |           click.shell_completion
import time:        85 |         85 |               shellingham._core
import time:        89 |        173 |             shellingham
import time:       217 |        390 |           typer._completion_shared
import time:       167 |        981 |         typer._completion_classes
import time:       599 |        599 |         typer.models
import time:       142 |        142 |         typer.params
import time:        36 |         36 |                 org
import time:         7 |         43 |               org.python
import time:         7 |         49 |             org.python.core
import time:        96 |        145 |           copy
import time:       121 |        266 |         typer.utils
import time:       131 |       2117 |       typer.completion
import time:       959 |        959 |       typer.core
import time:       574 |       9337 |     typer.main
import time:       151 |      24217 |   typer
import time:         9 |      24225 | typer.main

And here's a reasonable after:

import time: self [us] | cumulative | imported package
import time:       100 |        100 |   _io
import time:        17 |         17 |   marshal
import time:       177 |        177 |   posix
import time:       333 |        625 | _frozen_importlib_external
import time:        61 |         61 |   time
import time:        92 |        152 | zipimport
import time:        27 |         27 |     _codecs
import time:       269 |        296 |   codecs
import time:       188 |        188 |   encodings.aliases
import time:       331 |        814 | encodings
import time:        93 |         93 | encodings.utf_8
import time:        40 |         40 | _signal
import time:        25 |         25 |     _abc
import time:       157 |        181 |   abc
import time:       165 |        346 | io
import time:        30 |         30 |       _stat
import time:       104 |        134 |     stat
import time:       612 |        612 |     _collections_abc
import time:        87 |         87 |       genericpath
import time:       137 |        224 |     posixpath
import time:       457 |       1425 |   os
import time:       125 |        125 |   _sitebuiltins
import time:       270 |        270 |   _distutils_hack
import time:        40 |         40 |   sitecustomize
import time:        28 |         28 |   usercustomize
import time:       537 |       2422 | site
import time:       171 |        171 |             types
import time:       335 |        506 |           enum
import time:        37 |         37 |             _sre
import time:       522 |        522 |               sre_constants
import time:       192 |        714 |             sre_parse
import time:       143 |        893 |           sre_compile
import time:        53 |         53 |               itertools
import time:        69 |         69 |               keyword
import time:        44 |         44 |                 _operator
import time:       212 |        255 |               operator
import time:       164 |        164 |               reprlib
import time:        77 |         77 |               _collections
import time:       419 |       1035 |             collections
import time:        29 |         29 |             _functools
import time:       302 |       1366 |           functools
import time:        36 |         36 |           _locale
import time:       120 |        120 |           copyreg
import time:       299 |       3217 |         re
import time:        78 |       3294 |       fnmatch
import time:        40 |         40 |       errno
import time:       196 |        196 |       zlib
import time:       170 |        170 |         _compression
import time:       135 |        135 |         _bz2
import time:       129 |        433 |       bz2
import time:       160 |        160 |         _lzma
import time:       124 |        284 |       lzma
import time:       300 |       4546 |     shutil
import time:        78 |         78 |         __future__
import time:       136 |        136 |           collections.abc
import time:       457 |        457 |               _ast
import time:       413 |        413 |               contextlib
import time:       487 |       1355 |             ast
import time:       111 |        111 |                 _opcode
import time:       174 |        284 |               opcode
import time:       319 |        603 |             dis
import time:       136 |        136 |                 warnings
import time:       135 |        271 |               importlib
import time:       101 |        371 |             importlib.machinery
import time:        80 |         80 |                 token
import time:       481 |        560 |               tokenize
import time:        74 |        634 |             linecache
import time:       867 |       3828 |           inspect
import time:      1043 |       1043 |           typing
import time:       560 |        560 |           gettext
import time:       142 |        142 |               math
import time:       149 |        149 |               _datetime
import time:       456 |        746 |             datetime
import time:       150 |        150 |                 _weakrefset
import time:       198 |        348 |               weakref
import time:       225 |        572 |             click._compat
import time:       327 |        327 |                 threading
import time:        80 |        407 |               click.globals
import time:       181 |        181 |               click.utils
import time:       236 |        824 |             click.exceptions
import time:       786 |       2926 |           click.types
import time:       167 |        167 |           click._utils
import time:       179 |        179 |             click.parser
import time:       108 |        286 |           click.formatting
import time:       135 |        135 |           click.termui
import time:       601 |       9679 |         click.core
import time:       175 |        175 |         click.decorators
import time:       159 |      10089 |       click
import time:         8 |      10097 |     click.exceptions
import time:        86 |         86 |     typer.colors
import time:       433 |        433 |         signal
import time:       127 |        127 |         fcntl
import time:        41 |         41 |         msvcrt
import time:        78 |         78 |         _posixsubprocess
import time:        80 |         80 |         select
import time:       269 |        269 |         selectors
import time:       323 |       1349 |       subprocess
import time:       259 |        259 |       traceback
import time:        37 |         37 |           _winapi
import time:        32 |         32 |           nt
import time:        29 |         29 |           nt
import time:        28 |         28 |           nt
import time:        27 |         27 |           nt
import time:       123 |        274 |         ntpath
import time:        64 |         64 |           urllib
import time:       711 |        711 |           ipaddress
import time:       494 |       1269 |         urllib.parse
import time:       400 |       1942 |       pathlib
import time:      1121 |       1121 |         platform
import time:       165 |        165 |         _uuid
import time:       313 |       1599 |       uuid
import time:       123 |        123 |       typer._types
import time:       114 |        114 |       typer._typing
import time:        71 |         71 |             importlib._abc
import time:       115 |        186 |           importlib.util
import time:       166 |        166 |           click.shell_completion
import time:        82 |         82 |               shellingham._core
import time:        84 |        166 |             shellingham
import time:       208 |        374 |           typer._completion_shared
import time:       171 |        895 |         typer._completion_classes
import time:       646 |        646 |         typer.models
import time:       143 |        143 |         typer.params
import time:        36 |         36 |                 org
import time:         7 |         43 |               org.python
import time:         8 |         51 |             org.python.core
import time:        98 |        148 |           copy
import time:       124 |        272 |         typer.utils
import time:       173 |       2127 |       typer.completion
import time:       907 |        907 |       typer.core
import time:       455 |       8870 |     typer.main
import time:       102 |      23699 |   typer
import time:         8 |      23706 | typer.main

There is still a platform imported by uuid, but for some reason that is faster than having the import in main.py.