Common HTTP Client Functions for Python CLI

http_client.py

import argparse
import os
import sys
import urllib2
import json
import collections

# initialize the argParser with common arguments such as environment
def initArgParser(scriptDescription):
    parser = argparse.ArgumentParser(description=scriptDescription)
    parser.add_argument('--environment', '-e', metavar='TEST/PROD',
                       help='The environment to execute against.')
    parser.add_argument('--host', metavar='http((s)://host:port (if environment not defined))', 
                       help='If a specific host rather than environment is desired.')
    return parser 


# validate and parse the arguments and retrieve back an object containing the arguments
# Default arguments included are:
def validateAndGetArguments(argParser): 
    args = argParser.parse_args()
    #print args
    
    if args.host == None and args.environment == None:
        # no arguments passed in so let's try a system environment variable
        if os.environ['API_HOSTNAME'] != None:
            args.host = os.environ['API_HOSTNAME']
        else:
            print "ERROR: No hostname or environment defined."
            argParser.print_usage()
            sys.exit(-1)
            
    
    return args


# Return the the base URL configured for the environment defined by arguments
# For example: https://api-test.domain.com/
# Each script will append to this URL whatever suffix is desired and then pass it to createRequest.
def getBaseURL(args):
    # get hostname
    if args.host != None:
            url = args.host
    elif args.environment != None:
            if args.environment == 'PROD':
                    url = "https://api.domain.com/"
            elif args.environment == 'TEST':
                    url = "https://api-test.domain.com/"
    
    return url;

# Create the HTTP Request object for the given url and args.
# It sets up the defaults for security credentials and JSON types
# If the Content-Type needs to be different, override it on the request object returned from this method.
# For example:
#    request.add_header("Content-Type", "text/csv")
def createRequest(url, args, method):
    request = urllib2.Request(url)
    # headers and cookies
    request.add_header("Accept", "application/json")
    request.add_header("Content-Type", "application/json")
    request.add_header('Cookie', 'securityToken=' + args.securityToken)
    
    if method != None:
        # urllib2 somehow doesn't natively support setting methods so we override it
        request.get_method = lambda: method
    else:
        method = 'GET' # so we can use it in the curl command below
    
    if(args.outputCurl):
        print "Curl Command => "
        print "  curl -v -X " + method + " -H \"Accept:application/json\" -H \"Content-Type:application/json\" -w \"\\n\\n\" -b \"securityToken=" + args.securityToken + ";\" " + request.get_full_url()
        print ""    
    
    return request


# If a file is being posted, it can be added via this
def addFileToRequest(request, filePath):
    try:
        fileString = open(filePath).read()
    except Exception as e:
        print "Error => Can not read from file: " + filePath
        sys.exit(-1)
    
    # attach file
    request.add_data(fileString)

# Execute the request, perform error handling if needed and print out the result as formatted JSON.
def executeRequest(request):
    # execute request
    
    print "Executing " + request.get_method() + " => " + request.get_full_url() + " ..."
    print ""
    
    try:
        response = urllib2.urlopen(request)
    
        output = response.read()
        print "Success => Response Body:"
        print(json.dumps(json.loads(output, object_pairs_hook=collections.OrderedDict), indent=4))
        print ""
    except Exception as e:
    
        if hasattr(e, 'code'):
            print "Error => HTTP Status Code: " + str(e.code)
        else:
            print "Error => Unknown Exception Occurred: " + str(e)
        
        if hasattr(e, 'read'):
            errorOutput = e.read()
        
            try:
                print "Error => Response Body:"
                print ""
                print(json.dumps(json.loads(errorOutput, object_pairs_hook=collections.OrderedDict), indent=4))
                print ""
            except Exception as e2:
                print "Error => No JSON Response Body"