替換字符串，它的周圍是已知的，但該字符串的值是不知道的Python

Question

我有形式

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

這裏的字符串我不知道paranthesis之間的值（）。我想用其他日期替換這個日期。我如何用Python做到這一點？ 我想打開文件，然後使用語言的標準替換函數，但由於beween（）的值不知道，所以不可能。

這段代碼會有很多代碼，並且在這段代碼之後，因此用新行替換整行將不起作用，因爲它會覆蓋圍繞此代碼段的代碼。

Answer 1

如何使用正則表達式？運行後

TEMP.TXT

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" 

main.py

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) 

output.txt的：例如

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" 

Answer 2

就個人而言，我經常發現re.split（）來比re.sub（）更簡單。該重用凱文的代碼，並且將捕獲的一切，它（加上中間組），然後更換中間組：

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)) 

你可以吹掉捕獲中年組，但此時你在插入的東西名單。只是做一個更換更容易。

OTOH，這個特殊問題可能足夠小，不需要重錘。這裏是相同的代碼沒有重新：

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)