[Fixed]-Why does Django's `urlencode` not encode slash?

From the Django source, urlencode is basically a wrapper around Django’s urlquote utility method. From the comments in the source, urlquote is a UTF-8-safe version of urllib.quote.

So urlencode is using the same defaults as python’s urllib.quote, and the reason that urllib.quote does not escape slashes can be found in the documentation:

Replace special characters in string using the %xx escape. Letters,
digits, and the characters ‘_.-‘ are never quoted. By default, this
function is intended for quoting the path section of the URL. The
optional safe parameter specifies additional characters that should
not be quoted — its default value is ‘/’.

So, the reason is that it’s escaping the path, and '/' is a perfectly expected and valid character within a path.

To get urlencode to also escape / in a Django template, use {{ variable|urlencode:'' }}.

Explanation: The extra optional parameter tells urlencode the set of characters that are "safe", where the default is '/', so passing an empty string is telling urlencode that / is not safe and should be encoded.