为什么urllib.urlencode结果加上“25”？

Question

Python代码是：

user = "aabc" 
password = "yyy12%"
data = urllib.urlencode({"loginname": user, "nloginpwd": password})
print data

结果是：loginname=aabc&nloginpwd=yyy12%25

为什么25被添加到字符串的末尾？在

Answer 1

来自Wikipedia：

Because the percent ("%") character serves as the indicator for percent-encoded octets, it must be percent-encoded as "%25" for that octet to be used as data within a URI.

简单示例：

>>> urllib.parse.quote('%')
'%25'

Answer 2

%字符在URL中有特殊含义；它用于启动转义序列。请参阅维基百科上的Percent-encoding article。一个文本%也必须被编码，并且%25是编码版本。从维基百科页面：

Because the percent ("%") character serves as the indicator for percent-encoded octets, it must be percent-encoded as "%25" for that octet to be used as data within a URI.

换句话说，%25是一个编码的%字符。在