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Improve start-up time by deferring slow imports. #6

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Improve start-up time by deferring slow imports. #6

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1a70eb2
Improve start-up time by defering slow imports.
kalekundert Apr 9, 2020
a9f8e04
Defer a few more imports.
kalekundert Apr 10, 2020
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8 changes: 6 additions & 2 deletions configurator/config.py
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Original file line number Diff line number Diff line change
Expand Up @@ -16,8 +16,7 @@ class Config(ConfigNode):
"""

__slots__ = ('data', '_previous')

parsers = Parsers.from_entrypoints()
parsers = None

def __init__(self, data=None):
super(Config, self).__init__(data)
Expand Down Expand Up @@ -51,6 +50,11 @@ def from_stream(cls, stream, parser=None):
except ValueError:
pass
if not callable(parser):
# Loading the parsers takes a long time (≈200 ms) because it causes
# a lot of code to be imported (`pkg_resources`, `toml`, `yaml`,
# etc). So don't load the parsers until just before we need them.
if cls.parsers is None:
cls.parsers = Parsers.from_entrypoints()
parser = cls.parsers.get(parser)
return cls(parser(stream))

Expand Down
5 changes: 3 additions & 2 deletions configurator/parsers.py
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Original file line number Diff line number Diff line change
@@ -1,5 +1,3 @@
from pkg_resources import iter_entry_points


class ParseError(Exception):
"""
Expand All @@ -12,6 +10,9 @@ class Parsers(dict):

@classmethod
def from_entrypoints(cls):
# `pkg_resources` is slow to import, so defer until we need it.
from pkg_resources import iter_entry_points
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This is a bit ugly. Why is important pkg_resources so slow? Have you reported the issue upstream at https://github.com/pypa/setuptools?

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It is a bit ugly. I don't know why it's so slow, but there are already a couple issues open relating to this: pypa/setuptools#510 pypa/setuptools#926.


parsers = cls()
for entrypoint in iter_entry_points(group='configurator.parser'):
try:
Expand Down