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SF patch 670194: Performance enhancement for _strptime.py.

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From Brett Cannon.  Mostly speedups via caching format string ->
compiled regexp.
This commit is contained in:
Tim Peters 2003-01-19 04:40:44 +00:00
parent 6550051691
commit 80cebc16aa
1 changed files with 36 additions and 20 deletions
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56
Lib/_strptime.py
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@ -24,7 +24,6 @@ import locale
import calendar
from re import compile as re_compile
from re import IGNORECASE
from string import whitespace as whitespace_string
__author__ = "Brett Cannon"
__email__ = "drifty@bigfoot.com"
@ -33,6 +32,17 @@ __all__ = ['strptime']
RegexpType = type(re_compile(''))
def _getlang():
# Figure out what the current language is set to.
current_lang = locale.getlocale(locale.LC_TIME)[0]
if current_lang:
return current_lang
else:
current_lang = locale.getdefaultlocale()[0]
if current_lang:
return current_lang
else:
return ''
class LocaleTime(object):
"""Stores and handles locale-specific information related to time.
@ -285,19 +295,9 @@ class LocaleTime(object):
self.__timezone = self.__pad(time.tzname, 0)
def __calc_lang(self):
# Set self.__lang by using locale.getlocale() or
# locale.getdefaultlocale(). If both turn up empty, set the attribute
# to ''. This is to stop calls to this method and to make sure
# strptime() can produce an re object correctly.
current_lang = locale.getlocale(locale.LC_TIME)[0]
if current_lang:
self.__lang = current_lang
else:
current_lang = locale.getdefaultlocale()[0]
if current_lang:
self.__lang = current_lang
else:
self.__lang = ''
# Set self.__lang by using __getlang().
self.__lang = _getlang()
class TimeRE(dict):
@ -382,8 +382,8 @@ class TimeRE(dict):
def pattern(self, format):
"""Return re pattern for the format string."""
processed_format = ''
for whitespace in whitespace_string:
format = format.replace(whitespace, r'\s*')
whitespace_replacement = re_compile('\s+')
format = whitespace_replacement.sub('\s*', format)
while format.find('%') != -1:
directive_index = format.index('%')+1
processed_format = "%s%s%s" % (processed_format,
@ -394,15 +394,31 @@ class TimeRE(dict):
def compile(self, format):
"""Return a compiled re object for the format string."""
format = "(?#%s)%s" % (self.locale_time.lang,format)
return re_compile(self.pattern(format), IGNORECASE)
# Cached TimeRE; probably only need one instance ever so cache it for performance
_locale_cache = TimeRE()
# Cached regex objects; same reason as for TimeRE cache
_regex_cache = dict()
def strptime(data_string, format="%a %b %d %H:%M:%S %Y"):
"""Return a time struct based on the input data and the format string."""
locale_time = LocaleTime()
compiled_re = TimeRE(locale_time).compile(format)
found = compiled_re.match(data_string)
global _locale_cache
global _regex_cache
locale_time = _locale_cache.locale_time
# If the language changes, caches are invalidated, so clear them
if locale_time.lang != _getlang():
_locale_cache = TimeRE()
_regex_cache.clear()
format_regex = _regex_cache.get(format)
if not format_regex:
# Limit regex cache size to prevent major bloating of the module;
# The value 5 is arbitrary
if len(_regex_cache) > 5:
_regex_cache.clear()
format_regex = _locale_cache.compile(format)
_regex_cache[format] = format_regex
found = format_regex.match(data_string)
if not found:
raise ValueError("time data did not match format")
year = 1900