替换行中的字符串而不添加新行？

Question

我想替换包含patternB的行中的字符串，类似于：

发件人：

some lines
line contain patternA
some lines
line contain patternB
more lines

收件人：

some lines
line contain patternA
some lines
line contain patternB xx oo
more lines

我有这样的代码：

inputfile = open("d:\myfile.abc", "r")
outputfile = open("d:\myfile_renew.abc", "w")
obj = "yaya"
dummy = ""
item = []

for line in inputfile:
    dummy += line
    if line.find("patternA") != -1:
        for line in inputfile:
            dummy += line
            if line.find("patternB") != -1:
                item = line.split()
                dummy += item[0] + " xx " + item[-1] + "\n"
                break
outputfile.write(dummy)

它不会像预期的那样替换包含“patternB”的行，而是在它下面添加新行，如：

some lines
line contain patternA
some lines
line contain patternB
line contain patternB xx oo
more lines

我能用我的代码做什么？你知道吗

Answer 1

当然是这样，因为您在for循环的开头将行附加到dummy，然后在“if”语句中再次将修改后的版本附加到dummy。如果你像对待其他事物一样对待is，为什么还要检查模式A呢？你知道吗

inputfile = open("d:\myfile.abc", "r")
outputfile = open("d:\myfile_renew.abc", "w")
obj = "yaya"
dummy = ""
item = []

for line in inputfile:
    if line.find("patternB") != -1:
        item = line.split()
        dummy += item[0] + " xx " + item[-1] + "\n"
    else:
        dummy += line
outputfile.write(dummy)

Answer 2

最简单的方法是： 1将所有文件读入字符串 2呼叫字符串.替换 三。将字符串转储到文件

Answer 3

如果你想保持逐行迭代器 （对于大文件）

for line in inputfile:
    if line.find("patternB") != -1:
        dummy = line.replace('patternB', 'patternB xx oo')
        outputfile.write(dummy)
    else:
        outputfile.write(line)

这比其他响应慢，但支持大文件处理。你知道吗