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from packaging import version as _version
def _check_version(actver, version, cmp_op):
"""
Check version string of an active module against a required version.
If dev/prerelease tags result in TypeError for string-number comparison,
it is assumed that the dependency is satisfied.
Users on dev branches are responsible for keeping their own packages up to
date.
"""
try:
if cmp_op == '>':
return _version.parse(actver) > _version.parse(version)
elif cmp_op == '>=':
return _version.parse(actver) >= _version.parse(version)
elif cmp_op == '=':
return _version.parse(actver) == _version.parse(version)
elif cmp_op == '<':
return _version.parse(actver) < _version.parse(version)
else:
return False
except TypeError:
return True
def get_module_version(module_name):
"""Return module version or None if version can't be retrieved."""
mod = __import__(module_name, fromlist=[module_name.rpartition('.')[-1]])
return getattr(mod, '__version__', getattr(mod, 'VERSION', None))
def is_installed(name, version=None):
"""Test if *name* is installed.
Parameters
----------
name : str
Name of module or "python"
version : str, optional
Version string to test against.
If version is not None, checking version
(must have an attribute named '__version__' or 'VERSION')
Version may start with =, >=, > or < to specify the exact requirement
Returns
-------
out : bool
True if `name` is installed matching the optional version.
"""
if name.lower() == 'python':
actver = sys.version[:6]
else:
try:
actver = get_module_version(name)
except ImportError:
return False
if version is None:
return True
else:
# since version_requirements is in the critical import path,
# we lazy import re
import re
match = re.search('[0-9]', version)
assert match is not None, "Invalid version number"
symb = version[: match.start()]
if not symb:
symb = '='
assert symb in ('>=', '>', '=', '<'), f"Invalid version condition '{symb}'"
version = version[match.start() :]
return _check_version(actver, version, symb)
def require(name, version=None):
"""Return decorator that forces a requirement for a function or class.
Parameters
----------
name : str
Name of module or "python".
version : str, optional
Version string to test against.
If version is not None, checking version
(must have an attribute named '__version__' or 'VERSION')
Version may start with =, >=, > or < to specify the exact requirement
Returns
-------
func : function
A decorator that raises an ImportError if a function is run
in the absence of the input dependency.
"""
# since version_requirements is in the critical import path, we lazy import
# functools
import functools
def decorator(obj):
@functools.wraps(obj)
def func_wrapped(*args, **kwargs):
if is_installed(name, version):
return obj(*args, **kwargs)
else:
msg = f'"{obj}" in "{obj.__module__}" requires "{name}'
if version is not None:
msg += f" {version}"
raise ImportError(msg + '"')
return func_wrapped
return decorator
def get_module(module_name, version=None):
"""Return a module object of name *module_name* if installed.
Parameters
----------
module_name : str
Name of module.
version : str, optional
Version string to test against.
If version is not None, checking version
(must have an attribute named '__version__' or 'VERSION')
Version may start with =, >=, > or < to specify the exact requirement
Returns
-------
mod : module or None
Module if *module_name* is installed matching the optional version
or None otherwise.
"""
if not is_installed(module_name, version):
return None
return __import__(module_name, fromlist=[module_name.rpartition('.')[-1]])
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