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Code Issues 32 Releases Wiki Activity

Improved performance of django.template.base.Parser.

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pop(0), which is used to fetch each token, is O(n) in the length of the
list. By reversing the list and operating off the end, we can perform
next_token(), prepend_token(), and delete_first_token() in constant
time.
This commit is contained in:
Alex Gaynor 2019-10-08 22:25:20 -04:00 committed by Mariusz Felisiak
parent dafdfd6a60
commit 04ac9b45a3
1 changed files with 6 additions and 4 deletions
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10
django/template/base.py
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@ -405,7 +405,9 @@ class DebugLexer(Lexer):
class Parser: class Parser:
def __init__(self, tokens, libraries=None, builtins=None, origin=None): def __init__(self, tokens, libraries=None, builtins=None, origin=None):
self.tokens = tokens # Reverse the tokens so delete_first_token(), prepend_token(), and
# next_token() can operate at the end of the list in constant time.
self.tokens = list(reversed(tokens))
self.tags = {} self.tags = {}
self.filters = {} self.filters = {}
self.command_stack = [] self.command_stack = []
@ -541,13 +543,13 @@ class Parser:
raise self.error(token, msg) raise self.error(token, msg)
def next_token(self): def next_token(self):
return self.tokens.pop(0) return self.tokens.pop()
def prepend_token(self, token): def prepend_token(self, token):
self.tokens.insert(0, token) self.tokens.append(token)
def delete_first_token(self): def delete_first_token(self):
del self.tokens[0] del self.tokens[-1]
def add_library(self, lib): def add_library(self, lib):
self.tags.update(lib.tags) self.tags.update(lib.tags)