Question

当行与我的lookup_keyword匹配时，我想替换每一行上的字符。我设法找到了以下解决方案。但是 finaljoin 只会在新文件上写入更改（只有受影响的行被写回）

如何在新文件中一起编写未受影响的行？

我知道我们可以使用 fileinput inplace 编辑，但更适合关键字替换。

Example input file,
123456789 [Thanos]
123456789 [Thanos]
123456789 [Thor]
123456789 [Loki]

Example output file,
1AA345KK789 [Thanos]
1AA345KK789 [Thanos]



Expected output file that I actually wanted.
1AA345KK789 [Thanos]
1AA345KK789 [Thanos]
123456789 [Thor]
123456789 [Loki]




lookup_keyword= "Thanos"

with open(filename) as myFile:
    # myFile,1 means start reading the line at line number one.
    # By default python will read start from 0.
    for num, line in enumerate(myFile, 1):
        if lookup_keyword in line:
            #print ('Found at line:', num)
            s = list(line)
            s[1] = 'AA'
            s[5] = 'KK'

            # join the list to a original string form
            finaljoin = "".join(s)

            #print (finaljoin)
            with open(new_filename, 'a+') as f:
                f.write(finaljoin)

Answer 1

输出文件只包含您实际写入的行。

如果Thanos在该行中，则修改该行，打开输出文件，并将更改后的行附加到该行。

但如果没有，你什么都不做，所以什么也没写。

你可以这样解决：

for num, line in enumerate(myFile, 1):
    #print ('Found at line:', num)
    s = list(line)
    if lookup_keyword in line:
        s[1] = 'AA'
        s[5] = 'KK'
    # join the list to a original string form
    finaljoin = "".join(s)

    #print (finaljoin)
    with open(new_filename, 'a+') as f:
        f.write(finaljoin)

这样，无论您是否修改了新行，您都会创建新行并将其附加到新文件中。

可替换地：

for num, line in enumerate(myFile, 1):
    if lookup_keyword in line:
        #print ('Found at line:', num)
        s = list(line)
        s[1] = 'AA'
        s[5] = 'KK'

        # join the list to a original string form
        finaljoin = "".join(s)
    else:
        finaljoin = line
    with open(new_filename, 'a+') as f:
        f.write(finaljoin)

这样，当你不想修改它时，你不会浪费精力去分裂和重新加入这条线，而且它并没有那么复杂。

Answer 2

<强> input_file.txt

Example input file,
123456789 [Thanos]
123456789 [Thanos]
123456789 [Thor]
123456789 [Loki]

<强> Script.py

input_file_name = 'input_file.txt'
output_file_name = 'output_file.txt'

lookup_keyword= "Thanos"

with open(input_file_name) as input_file:
    next(input_file)        # skip first line
    with open(output_file_name, 'w') as output_file:
        for input_line in input_file:
            if lookup_keyword in input_line:
                input_list = list(input_line)
                input_list[1] = 'AA'
                input_list[5] = 'KK'

                output_line = ''.join(input_list)
            else:
                output_line = input_line

            output_file.write(output_line)

如何在不使用fileinput inplace的情况下更改python中的一行？

2 个答案: