python之如何将输出写入文件python

所以我有文件:data2.txt

Lollypop, 
Lolly pop, 
ooh  
lolly, 
lolly, lolly; 
lollypop, lollypop, 
ooh lolly, lolly, lolly, 
lollypop! 
ba dum dum dum ... 
 
LOL :-) 

我需要遍历 data2.txt 的每一行，只打印包含字符串 'lol' 的行，并将输出打印到新文件

with open("data3.txt") as g: 
    with open("data2.txt") as lfp: 
        for lin in lfp: 
            if 'lol' in lin: 
                g.write(str(lin)) 
            elif 'LOL' in lin: 
                g.write(str(lin)) 
            elif 'Lol' in lin: 
                g.write(str(lin)) 

但我不断收到错误:

    g.write(str(lin)) 
io.UnsupportedOperation: not writable 

请您参考如下方法:

写入需要用w打开:

with open("data3.txt","w") as g: 
    with open("data2.txt") as lfp: 

您还可以简化为:

with open("data3.txt", "w") as g, open("data2.txt") as lfp: 
        for lin in lfp: 
            if 'lol' in lin.lower(): 
                g.write(lin) 

或者使用写行:

with open("data3.txt", "w") as g, open("data2.txt") as lfp: 
        g.writelines(line for line in lfp if "lol" in line.lower()) 

line 已经是一个字符串，所以你不需要在它上面调用 str，在 line.lower() 中使用 "lol" 将匹配您所有的情况。

如果您要明确查找 "lol"、"Lol"、"LOL"，any 将是更好的方法。

with open("data3.txt", "w") as g, open("data2.txt") as lfp: 
    poss = ("lol", "Lol", "LOL") 
    g.writelines(line for line in lfp  
                    if any(s in line for s in poss)) 

所有模式都在 docs 中进行了解释