列表插入字典，却总被覆盖问题

django项目中遇到bug，总是遇到同一域名出现多个同一ip(域名和ip之间是多对多映射),后面检索到的域名覆盖前面域名,举例如下:

>>> listcontaindict=[{1:"a",2:"b"},{2:"b",3:"c"},{1:"a",3:"c"},{4:"d"}]
>>> tarlist=list()
>>> for line in listcontaindict:
...     if line.get(4) == "d":
...         line[5]="e"
...         tarlist.append(line)
... 
>>> tarlist
[{4: 'd', 5: 'e'}]
>>> for line in listcontaindict:
...     if line.get(4) == "d":
...         line[5]="f"
...         tarlist.append(line)
... 
>>> tarlist
[{4: 'd', 5: 'f'}, {4: 'd', 5: 'f'}]

问题原因:引用列表中字典的同一块内存地址引起
解决方案:

>>> tarlist=list()
>>> listcontaindict=[{1:"a",2:"b"},{2:"b",3:"c"},{1:"a",3:"c"},{4:"d"}]
>>> for line in listcontaindict:
...     if line.get(4) == "d":
...         lined=line.copy()
...         lined[5]="e"
...         tarlist.append(lined)
... 
>>> for line in listcontaindict:
...     if line.get(4) == "d":
...         lined=line.copy()
...         lined[5]="f"
...         tarlist.append(lined)
... 
>>> tarlist
[{4: 'd', 5: 'e'}, {4: 'd', 5: 'f'}]