Question

我是一名新的编码员，他在Python 3中接受了一些兼职培训，最近我给了一个家庭作业来编写一个程序，允许用户输入文件的名称，输入他们想要改变的文本。该文件，然后更改它。我写了一些代码，并正在试验＆＃34; r +＆＃34;功能，但我的代码似乎没有工作。我一直试图在我测试的.txt文件中更改的行不会改变如果有人能给我一些提示，我将非常感激。

# Build main

def main():
# Get file name and open for reading and writing
    toalter = input("Please enter a target file: ")
    infile = open(toalter, "r+")
# Get input of the line to be changed, and what it is to change to
    old = input("Please enter the text you want to change: ")
    new = input("Please enter what you want it changed to: ")

    for line in infile:
        if old in line:
            line = line.replace(old, new)
    infile.close()
main()

Answer 1

你用new替换了旧字符串，但是你从不调用语句将其写入＆＃34; toalter＆＃34;文件。
您无法同时打开文件进行读写，但您可以打开阅读，对该数据执行某些操作，然后再次打开以覆盖。

假设我有一个包含以下内容的test.txt文件。我想用椰子代替Apple。这就是我接近它的方式。

Apple
Orange
Strawberry
Kiwi

>>> def replace (old, new):
...     path = '/testfiles/test.txt'
...     with open (path) as f:
...         file = f.read ()
...     if old in file:
...         file = file.replace (old, new)
...     with open (path, 'w') as f:
...         f.write (file)
...         
>>> 
>>> replace ('Apple', 'Coconut')

<强>输出

Coconut
Orange
Strawberry
Kiwi

如果您的文件包含多个Apple实例，那么您需要将逻辑更改为此。

def replace (old, new):
...     newstring = ''
...     path = '/testfiles/test.txt'
...     with open (path) as f:
...         for line in f:
...             if old in line:
...                 newstring += line.replace (old, new)
...             else:
...                 newstring += line
...     with open (path, 'w') as f:
...         f.write (newstring)
...         
>>>

Python 3中的行替换

1 个答案: