Python 字典 : adding a value in a key already made without losing the original value

Question

我正在尝试在字典中添加一个 xml 文件。现在我想做的是在不丢失值的情况下将值更新到字典中。这样做的原因是我想对 xml 文件进行分组以显示标记作者所做的所有更改。

这是 xml 文件的示例。

<log> 
<logentry 
revision="33185"> 
<author>glv</author> 
<date>2012-08-06T21:01:52.494219Z</date> 
<paths> 

<path 
kind="file" 
action="M">/branches/Patch_4_2_0_Branch/text.xml</path>    

<path 
kind="dir" 
action="M">/branches/Patch_4_2_0_Branch</path> 

</paths> 
<msg>PATCH_BRANCH:N/A 
BUG_NUMBER:N/A 
FEATURE_AFFECTED:N/A 
OVERVIEW:N/A 
Adding the SVN log size requirement to the branch  
</msg> 
</logentry> 
 .... 
</log> 

这是我用 Python 编写的代码。

from xml.dom import minidom 
import smtplib 
from email.mime.text import MIMEText 
from datetime import datetime 

def xml_data (): 

f = open('C:\opidea_2.xml', 'r') 

data = f.read() 

f.close() 

dom = minidom.parseString(data) 

ic = (dom.getElementsByTagName('logentry')) 

dom = None       
content = '' 
author = {}   
for num in ic: 

authors = num.getElementsByTagName('author') 

if len(authors) > 0: 

  name = authors[0].firstChild.nodeValue 

  author.update({'author': str(name)})  

datef = [] 
xmlDate = num.getElementsByTagName('date')[0].firstChild.nodeValue 
datef = [Good_Time] 
path_change = []  
paths = [x for x in num.getElementsByTagName("paths")[0].childNodes if isinstance(x, minidom.Element)] 

for path in paths:  

  x = path.childNodes[0].nodeValue   

if str(path.getAttribute("kind")) == 'dir': 

  path_change ='Directory location: ' + [str(x)] 
else:  
  path_change ='Filename: ' + [str(x)] 

xmlMsgf = [] 
xmlMsg = num.getElementsByTagName('msg') 


if xmlMsg !='' and len(xmlMsg) > 0: 
  xmlMsgc = xmlMsg[0].firstChild.nodeValue 
  xmlMsgf = [xmlMsgc] 


 else: 
   xmlMsgc = "No comment made." 
   xmlMsgf = [xmlMsgc] 

 authorentry.push{('author',authorA),('date',datef),('path',path_change),('path',xmlMsgf))}           

    for k, v in [(authorentry)]:

        try:

            author[k].append(v)

        except KeyError:

            author[k] = [v]

 author.update({'Date':datef,'Path':path_change,'msg':str(xmlMsgf)}) 
 print author

if __name__ == "__main__": 
  xml_data () 

现在我想要的最终结果是这样的

Key 1 = glv , date1 ,path 1a path 1b , msg1 , date2 , path 2 , msg 2 , ...

key 2 = jsm, date1, path 1, msg 1.

我想将 author.update({'Date':datef,'Path':path_change,'msg':str(xmlMsgf)}) 分组以列出作者的 xml 文件以附加下一组内容作者做的。不太确定该怎么做。任何帮助，将不胜感激。这是我更新的代码，但我现在似乎收到了无效的语法错误:

  line 151
    authorentry.push{('author',authorA),('date',datef),('path',path_change),('path',xmlMsgf))}           
                    ^
 SyntaxError: invalid syntax

Answer 1

你不能在字典中“保留旧值”，每个键都有一个与之关联的值。

不过，您可以在字典中使用聚合值类型，例如，您可以使用列表作为值，并且每次您找到要添加的数据时，将其附加到关联列表中。

data = {}

for k, v in [('a', 1), ('a', 2), ('b', 3)]:
    try:
        data[k].append(v)
    except KeyError:
        data[k] = [v]  # a list of one element!

collections 模块中有一个方便的构造函数，可以使这更容易:

import collections

data = collections.defaultdict(list)
for k, v in [('a', 1), ('a', 2), ('b', 3)]:
    data[k].append(v)