替换行中的字符串而不添加新行？

Question

我想在包含patternB的行中替换字符串，如下所示：

从：

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

至：

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)

它不会按预期替换包含“ patternB”的行，而是在其下方添加新行，如下所示：

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

我该如何处理我的代码？

Answer 1

您可以使用str.replace ：

s = '''some lines
line contain patternA
some lines
line contain patternB
more lines'''

print(s.replace('patternB', 'patternB xx oo'))

Answer 2

最简单的方法是：1.将所有文件读入字符串2.调用string.replace 3.将字符串转储到文件

Answer 3

当然是这样，因为您在for循环的开头添加了对虚拟对象的行，然后在“ if”语句中再次添加了修改后的版本。 另外，如果您对待其他事物，为什么还要检查模式A？

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 4

如果要逐行保留迭代器（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)

这比其他响应速度慢，但可以处理大文件。

Answer 5

这应该工作

import os

def replace():

    f1 = open("d:\myfile.abc","r")
    f2 = open("d:\myfile_renew.abc","w")
    ow = raw_input("Enter word you wish to replace:")
    nw = raw_input("Enter new word:")
    for line in f1:
        templ = line.split()
        for i in templ:
            if i==ow:
                f2.write(nw)
            else:
                f2.write(i)
        f2.write('\n')
    f1.close()
    f2.close()
    os.remove("d:\myfile.abc")
    os.rename("d:\myfile_renew.abc","d:\myfile.abc")

replace()