如何将输出写入文件python

Question

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，仅打印包含字符串“ lol”的行，并将输出打印到新文件中

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))

但我不断出错：

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

Answer 1

您需要打开w进行编写：

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)

或使用writelines：

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，因此您不需要在其上调用str ， "lol" in line.lower()使用"lol" in line.lower()将满足您的所有情况。

如果您明确地寻找"lol", "Lol", "LOL" ，那么any都将是更好的方法。

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))

所有模式均在文档中进行了说明

Answer 2

问题出在with open("data3.txt") as g:的一行中with open("data3.txt") as g:

您未提供open模式，默认值为r ，仅用于读取。 使用with open("data3.txt", 'w') as g:如果要替换该文件（如果已存在），或者with open("data3.txt", 'a') as g:如果要如果文件已经存在，则追加到该文件。