【URL Quoting】
The URL quoting functions focus on taking program data and making it safe for use as URL components by quoting special characters and appropriately encoding non-ASCII text. They also support reversing these operations to recreate the original data from the contents of a URL component.
URL quoting函数作用是将数据能够作为url的一部分，包括处理特殊字符，及编码非ASCII文本。quoting函数也支持逆转以还原数据。
urllib.parse.quote(string, safe='/', encoding=None, errors=None)
Replace special characters in string using the %xx escape. Letters, digits, and the characters '_.-' are never quoted.
Note that quote(string, safe, encoding, errors) is equivalent to quote_from_bytes(string.encode(encoding, errors), safe).
Example: quote('/El Ni駉/') yields '/El%20Ni%C3%B1o/'.
urllib.parse.quote_plus(string, safe='', encoding=None, errors=None)- Like
quote(), but also replace spaces by plus signs, as required for quoting HTML form values when building up a query string to go into a URL. Plus signs in the original string are escaped unless they are included in safe. It also does not have safe default to'/'. - Example:
quote_plus('/El Ni駉/')yields'%2FEl+Ni%C3%B1o%2F'. - 在quote的基础上，把空格变为'+'，连'/'也会被转义。
urllib.parse.unquote(string, encoding='utf-8', errors='replace')- string must be a
str. - encoding defaults to
'utf-8'. errors defaults to'replace', meaning invalid sequences are replaced by a placeholder character. - Example:
unquote('/El%20Ni%C3%B1o/')yields'/El Ni駉/'.
urllib.parse.unquote_plus(string, encoding='utf-8', errors='replace')- Like
unquote(), but also replace plus signs by spaces, as required for unquoting HTML form values. - string must be a
str. - Example:
unquote_plus('/El+Ni%C3%B1o/')yields'/El Ni駉/'.
urllib.parse.urlencode(query, doseq=False, safe='', encoding=None, errors=None, quote_via=quote_plus)
Convert a mapping object or a sequence of two-element tuples, which may contain str or bytes objects, to a percent-encoded ASCII text string.
The resulting string is a series of key=value pairs separated by '&' characters, where both key and value are quoted using the quote_via function. By default, quote_plus() is used to quote the values, which means spaces are quoted as a '+' character and ‘/’ characters are encoded as %2F, which follows the standard for GET requests (application/x-www-form-urlencoded). An alternate function that can be passed as quote_via is quote(), which will encode spaces as %20 and not encode ‘/’ characters. For maximum control of what is quoted, use quote and specify a value for safe.
The safe, encoding, and errors parameters are passed down to quote_via (the encoding and errors parameters are only passed when a query element is a str).
To reverse this encoding process, parse_qs() and parse_qsl() are provided in this module to parse query strings into Python data structures.
【Example】
1、Here is an example session that uses the GET method to retrieve a URL containing parameters:
2、The following example uses the POST method instead. Note that params output from urlencode is encoded to bytes before it is sent to urlopen as data:
POST encode后的数据要转换为bytes！！！
3、The following example uses an explicitly specified HTTP proxy, overriding environment settings:
4、The following example uses an explicitly specified HTTP proxy, overriding environment settings:
