如果找到，则替换行或追加-python

我的文本是由“=”分隔的键值对。如果钥匙匹配，我想更换线路。如果没有，我想把它附加在底部。我尝试了几种方法，包括：

def split_command_key_and_value(command):
   if '=' in command:
      command2 = command.split('=')
      return command2

def test(command, path):
   command2 = split_command_key_and_value(command)
   pattern = command2[0]
   myfile = open(path,'r')  # open file handle for read
# use r'', you don't need to replace '\' with '/'
   result = open(path, 'w')  # open file handle for write
   for line in myfile:
      line = line.strip()  # it's always a good behave to strip what you read from files
      if pattern in line:
         line = command  # if match, replace line
      result.write(line)  # write every line
   myfile.close()  # don't forget to close file handle
   result.close()

我知道上面只是为了替换文本，但它删除了文件中的文本，我不明白为什么。有人能给我指出正确的方向吗

谢谢

更新：

我快到了，但是我的一些行有相似的键，所以当只有1行应该匹配时，多行是匹配的。我尝试在循环中加入正则表达式边界，但没有成功。我的代码如下。有人有什么建议吗

文件中有一些文本不是键值，所以我想跳过它

   def modify(self, name, value):
      comb = name + ' ' + '=' + ' ' + value + '\n'
      with open('/file/', 'w') as tmpstream:
         with open('/file/', 'r') as stream:
            for line in stream:
               if setting_name in line:
                  tmpstream.write(comb)
               else:
                  tmpstream.write(line)

我想我明白了。请参阅下面的代码

   def modify(self, name, value):
      comb = name + ' ' + '=' + ' ' + value + '\n'
      mylist = []
      with open('/file/', 'w') as tmpstream:
         with open('/file/', 'r') as stream:
            for line in stream:
               a = line.split()
               b = re.compile('\\b'+name+'\\b')
               if len(a) > 0:
                  if b.search(a[0]):
                     tmpstream.write(comb)
                  else:
                     tmpstream.write(line)

我说得太快了。它在我提供的键值处停止。所以，它只写一行，不写不匹配的行

def modify(name, value):
   comb = name + ' ' + '=' + ' ' + value + '\n'
   mylist = []
   with open('/file1', 'w') as tmpstream:
      with open('/file2', 'r') as stream:
         for line in stream:
            a = line.split()
            b = re.compile('\\b'+name+'\\b')
            if len(a) > 0:
               if b.search(a[0]):
                  tmpstream.write(comb)
            else:
              tmpstream.write(line)

---

有人能看到这个问题吗？

因为当您打开文件进行写入时

result = open(path, 'w')  # open file handle for write

你只要删除它的内容。尝试写入不同的文件，完成所有工作后，用新文件替换旧文件。或者将所有数据读入内存，然后进行处理并写入文件

with open(path) as f:
   data = f.read()
with open(path, 'w') as f:
   for l in data:
       # make job here

---

首先，你正在读一篇文章，写同一个文件。。。 你可以先把它全部读一遍，然后逐行写下来

with open(path,'r') as f:
   myfile = f.read() # read everything in the variable "myfile" 
result = open(path, 'w')  # open file handle for write
for line in myfile.splitlines(): # process the original file content 1 line at a time 
   # as before

---

我强烈建议您阅读python关于如何使用的文档

如果以写入模式打开现有文件

open（路径“w”）

，其内容将被擦除：

模式可以是（…）“w”仅用于写入（具有相同名称的现有文件将被擦除）

要替换python中的一行，可以查看以下内容：

这里有一个适合您环境的解决方案（针对python3进行了测试）：

---

请注意，使用上述代码，将替换与key（key=blob或blob=key）匹配的每一行。

您能提供一个输入示例吗？

from tempfile import mkstemp
from shutil import move
from os import close

def test(filepath, command):
    # Split command into key/value
    key, _ = command.split('=')
    matched_key = False

    # Create a temporary file
    fh, tmp_absolute_path = mkstemp()

    with open(tmp_absolute_path, 'w') as tmp_stream:
        with open(filepath, 'r') as stream:
            for line in stream:
                if key in line:
                    matched_key = True
                    tmp_stream.write(command + '\n')
                else:
                    tmp_stream.write(line)

        if not matched_key:
            tmp_stream.write(command + '\n')

    close(fh)
    move(tmp_absolute_path, filepath)