如何使用Python替换此文本中的冒号？

Question

我有一个文件，它看起来像

1::12::33::1555 
1::412::1245::23444 

等。我需要摆脱最后一个参数，并用逗号替换冒号。我曾尝试：

myfile = open('words.txt', 'r') 
    content = myfile.read() 
    content = re.sub(r'(.+)::(.+)::(.+)::(.+)', "\1,\2,\3", content) 
    myfile = open('words.txt', 'w') 
    myfile.write(content) 
    # Close the file 
    myfile.close() 

但后面的参考是不行的，我刚刚结束了与逗号文件..

就是我希望实现的是：

1,12,33 
1,412,1245 

Answer 1

这将使你的字符串，你需要：

line = '1::412::1245::23444' 
line_list = line.split('::') 
new_line = ','.join(line_list[:-1]) 

print new_line 
>> 1,412,1245 

Answer 2

反向引用只会插入一个原始字符串。

re.sub(r'(.+)::(.+)::(.+)::(.+)', r"\1,\2,\3", content) 

你也可以做到这一点使用纯字符串/列表

"\n".join([",".join(y.split('::')[:-1]) for y in content.split("\n")]) 

Answer 3

你可以只使用简单的字符串函数？

line = '1::412::1245::23444' 
s = s.replace('::',',') 
# content stored in a list 
content = s.split(',')[:-1] 

Answer 4

在Python 2.6：

with open('words.txt', 'r') as in_file: 
    with open('words_out.txt', 'w') as out_file: 
     for line in in_file: 
      new_line = ','.join(line.split('::')[:-1]) + ',' 
      out_file.write(new_line) 

在Python 2.7>

with open('words.txt', 'r') as in_file, open('words_out.txt', 'w') as out_file: 
    for line in in_file: 
     new_line = ','.join(line.split('::')[:-1]) + ',' 
     out_file.write(new_line) 

Answer 5

您可以使用CSV library像这样（为CSV嵌入CSV含蓄）：

import StringIO 
import csv 

t = """1::12::33::1555 
1::412::1245::23444""" 

f = StringIO.StringIO(t) 
reader = csv.reader(f, delimiter=':') 
for row in reader: 
    print ",".join(row[0:-1:2]) 

此输出：

1,12,33 
1,412,1245 

Answer 6

它看起来并不像你真正需要的正则表达式这一点。我会做的是将::作为分隔符分割线，然后删除最后一项并重新插入逗号。

myfile = open('words.txt', 'r') 
content = myfile.read() 
numbers = [int(s) for s in content.split("::")]  #get a list of numbers from the string 
numbers = numbers[0:-1]        #drop last number 
content = "".join([str(n) + ",," for n in numbers]) #coalesce numbers back to string 
myfile = open('words.txt', 'w') 
myfile.write(content) 
myfile.close()