import os
import sysconfig
def reset_tzpath(to=None):
global TZPATH
tzpaths = to
if tzpaths is not None:
if isinstance(tzpaths, (str, bytes)):
raise TypeError(
f"tzpaths must be a list or tuple, "
+ f"not {type(tzpaths)}: {tzpaths!r}"
)
if not all(map(os.path.isabs, tzpaths)):
raise ValueError(_get_invalid_paths_message(tzpaths))
base_tzpath = tzpaths
else:
env_var = os.environ.get("PYTHONTZPATH", None)
if env_var is not None:
base_tzpath = _parse_python_tzpath(env_var)
else:
base_tzpath = _parse_python_tzpath(
sysconfig.get_config_var("TZPATH")
)
TZPATH = tuple(base_tzpath)
def _parse_python_tzpath(env_var):
if not env_var:
return ()
raw_tzpath = env_var.split(os.pathsep)
new_tzpath = tuple(filter(os.path.isabs, raw_tzpath))
# If anything has been filtered out, we will warn about it
if len(new_tzpath) != len(raw_tzpath):
import warnings
msg = _get_invalid_paths_message(raw_tzpath)
warnings.warn(
"Invalid paths specified in PYTHONTZPATH environment variable. "
+ msg,
InvalidTZPathWarning,
)
return new_tzpath
def _get_invalid_paths_message(tzpaths):
invalid_paths = (path for path in tzpaths if not os.path.isabs(path))
prefix = "\n "
indented_str = prefix + prefix.join(invalid_paths)
return (
"Paths should be absolute but found the following relative paths:"
+ indented_str
)
def find_tzfile(key):
"""Retrieve the path to a TZif file from a key."""
_validate_tzfile_path(key)
for search_path in TZPATH:
filepath = os.path.join(search_path, key)
if os.path.isfile(filepath):
return filepath
return None
_TEST_PATH = os.path.normpath(os.path.join("_", "_"))[:-1]
def _validate_tzfile_path(path, _base=_TEST_PATH):
if os.path.isabs(path):
raise ValueError(
f"ZoneInfo keys may not be absolute paths, got: {path}"
)
# We only care about the kinds of path normalizations that would change the
# length of the key - e.g. a/../b -> a/b, or a/b/ -> a/b. On Windows,
# normpath will also change from a/b to a\b, but that would still preserve
# the length.
new_path = os.path.normpath(path)
if len(new_path) != len(path):
raise ValueError(
f"ZoneInfo keys must be normalized relative paths, got: {path}"
)
resolved = os.path.normpath(os.path.join(_base, new_path))
if not resolved.startswith(_base):
raise ValueError(
f"ZoneInfo keys must refer to subdirectories of TZPATH, got: {path}"
)
del _TEST_PATH
def available_timezones():
"""Returns a set containing all available time zones.
.. caution::
This may attempt to open a large number of files, since the best way to
determine if a given file on the time zone search path is to open it
and check for the "magic string" at the beginning.
"""
from importlib import resources
valid_zones = set()
# Start with loading from the tzdata package if it exists: this has a
# pre-assembled list of zones that only requires opening one file.
try:
with resources.open_text("tzdata", "zones") as f:
for zone in f:
zone = zone.strip()
if zone:
valid_zones.add(zone)
except (ImportError, FileNotFoundError):
pass
def valid_key(fpath):
try:
with open(fpath, "rb") as f:
return f.read(4) == b"TZif"
except Exception: # pragma: nocover
return False
for tz_root in TZPATH:
if not os.path.exists(tz_root):
continue
for root, dirnames, files in os.walk(tz_root):
if root == tz_root:
# right/ and posix/ are special directories and shouldn't be
# included in the output of available zones
if "right" in dirnames:
dirnames.remove("right")
if "posix" in dirnames:
dirnames.remove("posix")
for file in files:
fpath = os.path.join(root, file)
key = os.path.relpath(fpath, start=tz_root)
if os.sep != "/": # pragma: nocover
key = key.replace(os.sep, "/")
if not key or key in valid_zones:
continue
if valid_key(fpath):
valid_zones.add(key)
if "posixrules" in valid_zones:
# posixrules is a special symlink-only time zone where it exists, it
# should not be included in the output
valid_zones.remove("posixrules")
return valid_zones
class InvalidTZPathWarning(RuntimeWarning):
"""Warning raised if an invalid path is specified in PYTHONTZPATH."""
TZPATH = ()
reset_tzpath()