How to urlencode a querystring in Python?

Question

I am trying to urlencode this string before I submit.

queryString = \'eventName=\' + evt.fields[\"eventName\"] + \'&\' + \'eventDescription=\' + evt.fie         


        

Answer 1

Context

• Python (version 2.7.2 )

Problem

• You want to generate a urlencoded query string.
• You have a dictionary or object containing the name-value pairs.
• You want to be able to control the output ordering of the name-value pairs.

Solution

• urllib.urlencode
• urllib.quote_plus

Pitfalls

• dictionary output arbitrary ordering of name-value pairs
  • (see also: Why is python ordering my dictionary like so?)
  • (see also: Why is the order in dictionaries and sets arbitrary?)
• handling cases when you DO NOT care about the ordering of the name-value pairs
• handling cases when you DO care about the ordering of the name-value pairs
• handling cases where a single name needs to appear more than once in the set of all name-value pairs

Example

The following is a complete solution, including how to deal with some pitfalls.

### ********************
## init python (version 2.7.2 )
import urllib

### ********************
## first setup a dictionary of name-value pairs
dict_name_value_pairs = {
  "bravo"   : "True != False",
  "alpha"   : "http://www.example.com",
  "charlie" : "hello world",
  "delta"   : "1234567 !@#$%^&*",
  "echo"    : "user@example.com",
  }

### ********************
## setup an exact ordering for the name-value pairs
ary_ordered_names = []
ary_ordered_names.append('alpha')
ary_ordered_names.append('bravo')
ary_ordered_names.append('charlie')
ary_ordered_names.append('delta')
ary_ordered_names.append('echo')

### ********************
## show the output results
if('NO we DO NOT care about the ordering of name-value pairs'):
  queryString  = urllib.urlencode(dict_name_value_pairs)
  print queryString 
  """
  echo=user%40example.com&bravo=True+%21%3D+False&delta=1234567+%21%40%23%24%25%5E%26%2A&charlie=hello+world&alpha=http%3A%2F%2Fwww.example.com
  """

if('YES we DO care about the ordering of name-value pairs'):
  queryString  = "&".join( [ item+'='+urllib.quote_plus(dict_name_value_pairs[item]) for item in ary_ordered_names ] )
  print queryString
  """
  alpha=http%3A%2F%2Fwww.example.com&bravo=True+%21%3D+False&charlie=hello+world&delta=1234567+%21%40%23%24%25%5E%26%2A&echo=user%40example.com
  """