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# -*- mode: python; -*-
# Try to keep this modules imports minimum and only
# import python standard modules, because this module
# should be used for finding such external modules or
# missing dependencies.
import sys
class MissingRequirements(Exception):
"""Raised when when verify_requirements() detects missing requirements."""
pass
def verify_requirements(requirements_file: str, silent: bool = False, executable=sys.executable):
"""Check if the modules in a pip requirements file are installed.
This allows for a more friendly user message with guidance on how to
resolve the missing dependencies.
Args:
requirements_file: path to a pip requirements file.
silent: True if the function should print.
Raises:
MissingRequirements if any requirements are missing
"""
def verbose(*args, **kwargs):
if not silent:
print(*args, **kwargs)
def raiseSuggestion(ex, pip_pkg):
raise MissingRequirements(f"{ex}\n"
f"Try running:\n"
f" {executable} -m pip install {pip_pkg}") from ex
# Import the prequisites for this function, providing hints on failure.
try:
import requirements
except ModuleNotFoundError as ex:
raiseSuggestion(ex, "requirements_parser")
try:
import pkg_resources
except ModuleNotFoundError as ex:
raiseSuggestion(ex, "setuptools")
verbose("Checking required python packages...")
# Reduce a pip requirements file to its PEP 508 requirement specifiers.
with open(requirements_file) as fd:
pip_lines = [p.line for p in requirements.parse(fd)]
# The PEP 508 requirement specifiers can be parsed by the `pkg_resources`.
pkg_requirements = list(pkg_resources.parse_requirements(pip_lines))
verbose("Requirements list:")
for req in sorted(set([str(req) for req in pkg_requirements])):
verbose(f" {req}")
# Resolve all the requirements at once.
# This should help expose dependency hell among the requirements.
try:
dists = pkg_resources.working_set.resolve(pkg_requirements)
except pkg_resources.ResolutionError as ex:
raiseSuggestion(
ex,
f"-r {requirements_file}",
)
verbose("Resolved to these distributions:")
for dist in sorted(set([f" {dist.key} {dist.version}" for dist in dists])):
verbose(dist)
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