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 f

input.txt 包含：

a
d
c
b
e
f
g
a
a

output.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=False

for 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 output 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')