替换环境已知但字符串值未知的字符串

Question

我有一个字符串的形式

**var beforeDate = new Date('2015-08-21')**

这里我不知道paranethesis（）之间的值。我想用其他日期代替这个日期。我怎样才能用Python来做呢？ 我想打开文件，然后使用该语言的标准replace函数，但是由于beween（）的值未知，所以这是不可能的。你知道吗

这个代码段以及这个代码段之后会有很多代码，所以用新行替换整行代码是行不通的，因为它会覆盖这个代码段周围的代码。你知道吗

Answer 1

就我个人而言，我通常重新拆分（）使用起来比回复sub(). 这将重用Kevin的代码，并将捕获它所做的一切（加上中间组），然后替换中间组：

import re

new_value = "'1999-12-31'"
with open("temp.txt") as infile:
    data = infile.read()

data = re.split(r"(var beforeDate = new Date\()(.*?)(\))", data)
# data[0] is everything before the first capture
# data[1] is the first capture
# data[2] is the second capture   the one we want to replace
data[2] = new_value

with open("output.txt", "w") as outfile:
    outfile.write(''.join(stuff))

你可以放弃捕获中间组，但你会在列表中插入内容。换个地方比较容易。你知道吗

奥托，这个问题可能很小，不需要重锤。以下是相同的代码，没有re：

new_value = "'1999-12-31'"
with open("temp.txt") as infile:
    data = infile.read()

data = list(data.partition('var beforeDate = new Date('))
data += data.pop().partition(')')
data[2] = new_value

with open("output.txt", "w") as outfile:
    for stuff in data:
        outfile.write(stuff)

Answer 2

用正则表达式怎么样？示例：

你知道吗温度.txt你知道吗

print "I've got a lovely bunch of coconuts"
var beforeDate = new Date('2015-08-21') #date determined by fair die roll
print "Here they are, standing in a row"

你知道吗主.py你知道吗

import re

new_value = "'1999-12-31'"
with open("temp.txt") as infile:
    data = infile.read()
    data = re.sub(r"(var beforeDate = new Date\().*?(\))", "\\1"+new_value+"\\2", data)
with open("output.txt", "w") as outfile:
    outfile.write(data)

你知道吗输出.txt运行后：

print "I've got a lovely bunch of coconuts"
var beforeDate = new Date('1999-12-31') #date determined by fair die roll
print "Here they are, standing in a row"