纯洁美丽。它化做雪花,用自己洁白的生躯覆盖在大地上。此时,一切都是银装素裹,一副冰清玉洁的模样。光秃秃的树枝上缀满了朵朵洁白的 "梨花 ",风一吹,花儿纷纷飘落,好似一只只银白色的蝴蝶在空中偏偏起舞。 "忽如一夜春风来,千树万树梨花开 ",这句诗不正是赞美冬天的吗?
定制pattern的string模板(template) 详解
string.Template的pattern是一个正则表达式, 可以通过覆盖pattern属性, 定义新的正则表达式.
如: 使用新的定界符"{{", 把{{var}}作为变量语法.
代码:
# -*- coding: utf-8 -*-
'''''
Created on 2014.6.5
@author: Administrator
@edition : python 3.3.0, eclipse pydev
'''
import string
t = string.Template('$var')
print(t.pattern.pattern)
class MyTemplate(string.Template):
delimiter = '{{'
pattern = r'''''
\{\{(?:
(?P<escaped>\{\{) | # Escape sequence of two delimiters
(?P<named>[_a-z][_a-z0-9]*)\}\} | # delimiter and a Python identifier
{(?P<braced>[_a-z][_a-z0-9]*)}\}\} | # delimiter and a braced identifier
(?P<invalid>) # Other ill-formed delimiter exprs
)
'''
t2 = MyTemplate('''''
{{{{
{{var}}
''')
print('MATCHES: ', t2.pattern.findall(t2.template))
print('SUBSTITUTED: ', t2.safe_substitute(var='replacement'))
输出:
\$(?:
(?P<escaped>\$) | # Escape sequence of two delimiters
(?P<named>[_a-z][_a-z0-9]*) | # delimiter and a Python identifier
{(?P<braced>[_a-z][_a-z0-9]*)} | # delimiter and a braced identifier
(?P<invalid>) # Other ill-formed delimiter exprs
)
MATCHES: [('{{', '', '', ''), ('', 'var', '', '')]
SUBSTITUTED:
{{
replacement
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