如何在python中编写文件时跳过文本块

Question

从其他文件写入文件时，是否可以使用python跳过文本块？

例如，假设输入文件为：

This is the file I would like to write this line
I would like to skip this line
and this one...
and this one...
and this one...
but I want to write this one
and this one...

如何编写一个脚本，允许我跳过某些内容和大小不同的行，一旦识别出某一行，就会恢复将行写入另一个文件？

修改

我的代码通过行读取，不会写行重复行，并使用字典和正则表达式对行执行某些操作。

Answer 1

def is_wanted(line):
    #
    # You have to define this!
    #
    # return True to keep the line, or False to discard it

def copy_some_lines(infname, outfname, wanted_fn=is_wanted):
    with open(infname) as inf, open(outfname, "w") as outf:
        outf.writelines(line for line in inf if wanted_fn(line))

copy_some_lines("file_a.txt", "some_of_a.txt")

---

为了将其扩展为多行块，您可以实现像

这样的有限状态机

会变成类似

的东西

class BlockState:
    GOOD_BLOCK = True
    BAD_BLOCK = False

    def __init__(self):
        self.state = self.GOOD_BLOCK

    def is_bad(self, line):
        # *** Implement this! ***
        # return True if line is bad

    def is_good(self, line):
        # *** Implement this! ***
        # return True if line is good

    def __call__(self, line):
        if self.state == self.GOOD_BLOCK:
            if self.is_bad(line):
                self.state = self.BAD_BLOCK
        else:
            if self.is_good(line):
                self.state = self.GOOD_BLOCK
        return self.state

然后

copy_some_lines("file_a.txt", "some_of_a.txt", BlockState())

Answer 2

的伪代码：

# Open input and output files, and declare the unwanted function
for line in file1:
    if unwanted(line):
        continue
    file2.write(line)
# Close files etc...

Answer 3

您可以逐行阅读文件，并控制您阅读的每一行：

with open(<your_file>, 'r') as lines:
    for line in lines:
        # skip this line
        # but not this one

请注意，如果您想要读取所有内容，只有内容然后才能操作它，您可以：

with open(<your_file>) as fil:
    lines = fil.readlines()

Answer 4

这应该有效：

SIZE_TO_SKIP = ?
CONTENT_TO_SKIP = "skip it"

with open("my/input/file") as input_file:
    with open("my/output/file",'w') as output_file:
        for line in input_file:
            if len(line)!=SIZE_TO_SKIP and line!=CONTENT_TO_SKIP:
                output_file.write(line)