如何跳过文本文件中的某些行并继续阅读python中的下一行？

Question

我一直在寻找这个答案，但不太明白。

我有一个像这样的文本文件

who are you????
who are you man?
who are you!!!!
who are you? man or woman?

我想跳过带有man 的行并打印

who are you????
who are you!!!!

到目前为止我的代码

f = open("test.txt", "r")
word = "man"
for line in f:
    if word in line:
        f.next()
    else:
        print line

这只会打印第一行

who are you????

我应该如何解决这个问题？

感谢您的帮助。

Answer 1

for循环中不需要添加if else语句，可以这样修改代码：

f = open("test.txt", "r")
word = "man"
for line in f:
    if not word in line:
        print line

此外，您的代码中的问题是您在用于扫描文件的 for 循环中直接使用 f.next()。这是因为当该行包含“man”字样时，您的代码会跳过两行。

如果您想保留if else 语句，因为这只是一个更复杂问题的示例，您可以使用以下代码：

f = open("test.txt", "r")
word = "man"
for line in f:
    if word in line:
        continue
    else:
        print line

使用continue，您可以跳过一个循环的迭代，从而达到您的目标。

正如 Alex Fung 所建议的，最好使用with，所以你的代码会变成这样：

with open("test.txt", "r") as test_file:
    for line in test_file:
        if "man" not in line:
            print line

Answer 2

怎么样

f = open("test.txt", "r")
word = "man"
for line in f:
    if not word in line:
        print line

Answer 3

问题

使用您当前的代码，当当前行包含 "man" 时：

• 您不打印任何内容。没错。
• 您也跳过了下一行。那是你的问题！
• f.next() 已经在每次迭代中被 for line in f: 隐式调用。因此，当找到“man”时，您实际上调用了两次 f.next()。
• 如果文件的最后一行包含"man"，Python 将抛出异常，因为没有下一行。

您可能一直在寻找continue，它也可以达到预期的效果，但会很复杂且不需要。请注意，它在 Perl 和 Ruby 中称为 next，这可能会造成混淆。

示例

who are you????            # <- This line gets printed, because there's no "man" in it
who are you man?           # word in line is True. Don't print anything. And skip next line
who are you!!!!            # Line is skipped because of f.next()
who are you? man or woman? # word in line is True. Don't print anything. 
                           #   Try to skip next line, but there's no next line anymore.
                           #   The script raises an exception : StopIteration

正确的代码

不要忘记关闭文件。您可以使用 with 自动执行此操作：

word = "man"
with open("test.txt") as f:
    for line in f:
        if not word in line:
            print line, # <- Note the comma to avoid double newlines