Source code for requests_cache.policy.expiration

"""Utility functions for parsing and converting expiration values"""
from datetime import datetime, timedelta, timezone
from email.utils import parsedate_to_datetime
from fnmatch import fnmatch
from logging import getLogger
from math import ceil
from typing import Optional
from typing import Pattern as RegexPattern

from .._utils import try_int
from . import ExpirationPattern, ExpirationPatterns, ExpirationTime

# Special expiration values that may be set by either headers or keyword args
DO_NOT_CACHE = 0x0D0E0200020704  # Per RFC 4824

logger = getLogger(__name__)

[docs]def get_expiration_datetime( expire_after: ExpirationTime, start_time: Optional[datetime] = None, negative_delta: bool = False, ignore_invalid_httpdate: bool = False, ) -> Optional[datetime]: """Convert an expiration value in any supported format to an absolute datetime""" # Never expire (or do not cache, in which case expiration won't be used) if expire_after is None or expire_after in [NEVER_EXPIRE, DO_NOT_CACHE]: return None # Expire immediately elif try_int(expire_after) == EXPIRE_IMMEDIATELY: return start_time or utcnow() # Already a datetime or httpdate str (allowed for headers only) if isinstance(expire_after, str): expire_after_dt = _parse_http_date(expire_after) if not expire_after_dt and not ignore_invalid_httpdate: raise ValueError(f'Invalid HTTP date: {expire_after}') return expire_after_dt elif isinstance(expire_after, datetime): return expire_after.astimezone(timezone.utc) # Otherwise, it must be a timedelta or time in seconds if not isinstance(expire_after, timedelta): expire_after = timedelta(seconds=expire_after) if negative_delta: expire_after = -expire_after return (start_time or utcnow()) + expire_after
[docs]def get_expiration_seconds(expire_after: ExpirationTime) -> int: """Convert an expiration value in any supported format to an expiration time in seconds""" if expire_after == DO_NOT_CACHE: return DO_NOT_CACHE expires = get_expiration_datetime(expire_after, ignore_invalid_httpdate=True) return ceil((expires - utcnow()).total_seconds()) if expires else NEVER_EXPIRE
[docs]def get_url_expiration( url: Optional[str], urls_expire_after: Optional[ExpirationPatterns] = None ) -> ExpirationTime: """Check for a matching per-URL expiration, if any""" if not url: return None for pattern, expire_after in (urls_expire_after or {}).items(): if _url_match(url, pattern): logger.debug(f'URL {url} matched pattern "{pattern}": {expire_after}') return expire_after return None
[docs]def add_tzinfo(dt: Optional[datetime]) -> Optional[datetime]: """Add a UTC timezone to a datetime object, if it doesn't already have one. This is used mainly during deserialization for backends that don't store timezone info. """ if dt and dt.tzinfo is None: return dt.replace(tzinfo=timezone.utc) return dt
[docs]def utcnow() -> datetime: """Get the current time in UTC (timezone-aware)""" return
def _parse_http_date(value: str) -> Optional[datetime]: """Attempt to parse an HTTP (RFC 5322-compatible) timestamp""" try: expire_after = parsedate_to_datetime(value) return expire_after.astimezone(timezone.utc) except (TypeError, ValueError): logger.debug(f'Failed to parse timestamp: {value}') return None def _url_match(url: str, pattern: ExpirationPattern) -> bool: """Determine if a URL matches a pattern Args: url: URL to test. Its base URL (without protocol) will be used. pattern: Glob pattern to match against. A recursive wildcard will be added if not present Example: >>> url_match('', '') True >>> url_match('', '*/1') True >>> url_match('', '*/1') False >>> url_match('', re.compile('*/\\d+')) True >>> url_match('', re.compile('*/\\d+')) False """ if isinstance(pattern, RegexPattern): match = return match is not None else: url = url.split('://')[-1] pattern = pattern.split('://')[-1].rstrip('*') + '**' return fnmatch(url, pattern)