如何在python中将文本的某一部分从一个文件复制到另一个文件

Question

要在此示例中提取文本的某个部分，我想从 d 提取到 finput.txt 包含：adcbefgaaoutput.txt 应该包含从 d 到 f 但这个程序从 d 复制到 input.txt 文件的最后一行f = open('input.txt')f1 = open('output.txt', 'a')intermediate_variable=Falsefor line in f:    if 'd' in line:        intermediate_variable=True        if intermediate_variable==True:            f1.write(line)f1.close()f.close()

Answer 1

我认为应该这样做：

contents = open('input.txt').read()

f1.write(contents[contents.index("d"):contents.index("f")])

Answer 2

有更方便的方式来读写文件，这个版本使用了一个生成器和'with'关键字（上下文管理器），它会自动为你关闭文件。生成器（带有 'yield' 的函数很好，因为它们一次给你一行文件，尽管你必须将它们的输出包装在 try/except 块中）

def reader(filename):

    with open(filename, 'r') as fin:

        for line in fin:

            yield line

def writer(filename, data):

    with open(filename, 'w') as fout:  #change 'w' to 'a' to append ('w' overwrites)

        fout.write(data)

if __name__ == "__main__":

    a = reader("input.txt")

    while True:

        try:

            temp = next(a)

            if 'd' in temp:

                #this version of above answer captures the 'f' as well

                writer("output.txt", temp[temp.index('d'):temp.index('f') + 1])

        except StopIteration:

            break

Answer 3

直截了当：

### load all the data at once, fine for small files:

with open('input.txt', 'r') as f:

    content = f.read().splitlines() ## use f.readlines() to have the newline chars included

### slice what you need from content:

selection = content[content.index("d"):content.index("f")]

## use content.index("f")+1 to include "f" in the output.

### write selection to output:

with open('output.txt', 'a') as f:

    f.write('\n'.join(selection))

    ## or:

    # for line in selection:

        # f.write(line + '\n')