new_contents: # AWS Version 4 signing example
  
  # IAM API (CreateUser)
  
  # See: http://docs.aws.amazon.com/general/latest/gr/sigv4_signing.html
  # This version makes a GET request and passes request parameters
  # and authorization information in the query string
  import sys, os, base64, datetime, hashlib, hmac, urllib
  import requests # pip install requests
  
  # ************* REQUEST VALUES *************
  method = 'GET'
  service = 'iam'
  host = 'iam.amazonaws.com'
  region = 'us-east-1'
  endpoint = 'https://iam.amazonaws.com'
  
  # Key derivation functions. See:
  # http://docs.aws.amazon.com/general/latest/gr/signature-v4-examples.html#signature-v4-examples-python
  def sign(key, msg):
      return hmac.new(key, msg.encode('utf-8'), hashlib.sha256).digest()
  
  def getSignatureKey(key, dateStamp, regionName, serviceName):
      kDate = sign(('AWS4' + key).encode('utf-8'), dateStamp)
      kRegion = sign(kDate, regionName)
      kService = sign(kRegion, serviceName)
      kSigning = sign(kService, 'aws4_request')
      return kSigning
  
  # Read AWS access key from env. variables or configuration file. Best practice is NOT
  # to embed credentials in code.
  access_key = os.environ.get('AWS_ACCESS_KEY_ID')
  secret_key = os.environ.get('AWS_SECRET_ACCESS_KEY')
  if access_key is None or secret_key is None:
      print 'No access key is available.'
      sys.exit()
  
  # Create a date for headers and the credential string
  t = datetime.datetime.utcnow()
  amz_date = t.strftime('%Y%m%dT%H%M%SZ') # Format date as YYYYMMDD'T'HHMMSS'Z'
  datestamp = t.strftime('%Y%m%d') # Date w/o time, used in credential scope
  
  
  # ************* TASK 1: CREATE A CANONICAL REQUEST *************
  # http://docs.aws.amazon.com/general/latest/gr/sigv4-create-canonical-request.html
  
  # Because almost all information is being passed in the query string,
  # the order of these steps is slightly different than examples that
  # use an authorization header.
  
  # Step 1: Define the verb (GET, POST, etc.)--already done.
  
  # Step 2: Create canonical URI--the part of the URI from domain to query
  # string (use '/' if no path)
  canonical_uri = '/'
  
  # Step 3: Create the canonical headers and signed headers. Header names
  # and value must be trimmed and lowercase, and sorted in ASCII order.
  # Note trailing \n in canonical_headers.
  # signed_headers is the list of headers that are being included
  # as part of the signing process. For requests that use query strings,
  # only "host" is included in the signed headers.
  canonical_headers = 'host:' + host + '\n'
  signed_headers = 'host'
  
  # Match the algorithm to the hashing algorithm you use, either SHA-1 or
  # SHA-256 (recommended)
  algorithm = 'AWS4-HMAC-SHA256'
  credential_scope = datestamp + '/' + region + '/' + service + '/' + 'aws4_request'
  
  # Step 4: Create the canonical query string. In this example, request
  # parameters are in the query string. Query string values must
  # be URL-encoded (space=%20). The parameters must be sorted by name.
  canonical_querystring = 'Action=CreateUser&UserName=NewUser&Version=2010-05-08'
  canonical_querystring += '&X-Amz-Algorithm=AWS4-HMAC-SHA256'
  canonical_querystring += '&X-Amz-Credential=' + urllib.quote_plus(access_key + '/' + credential_scope)
  canonical_querystring += '&X-Amz-Date=' + amz_date
  canonical_querystring += '&X-Amz-Expires=30'
  canonical_querystring += '&X-Amz-SignedHeaders=' + signed_headers
  
  # Step 5: Create payload hash. For GET requests, the payload is an
  # empty string ("").
  payload_hash = hashlib.sha256('').hexdigest()
  
  # Step 6: Combine elements to create create canonical request
  canonical_request = method + '\n' + canonical_uri + '\n' + canonical_querystring + '\n' + canonical_headers + '\n' + signed_headers + '\n' + payload_hash
  
  
  # ************* TASK 2: CREATE THE STRING TO SIGN*************
  string_to_sign = algorithm + '\n' +  amz_date + '\n' +  credential_scope + '\n' +  hashlib.sha256(canonical_request).hexdigest()
  
  
  # ************* TASK 3: CALCULATE THE SIGNATURE *************
  # Create the signing key
  signing_key = getSignatureKey(secret_key, datestamp, region, service)
  
  # Sign the string_to_sign using the signing_key
  signature = hmac.new(signing_key, (string_to_sign).encode("utf-8"), hashlib.sha256).hexdigest()
  
  
  # ************* TASK 4: ADD SIGNING INFORMATION TO THE REQUEST *************
  # The auth information can be either in a query string
  # value or in a header named Authorization. This code shows how to put
  # everything into a query string.
  canonical_querystring += '&X-Amz-Signature=' + signature
  
  
  # ************* SEND THE REQUEST *************
  # The 'host' header is added automatically by the Python 'request' lib. But it
  # must exist as a header in the request.
  request_url = endpoint + "?" + canonical_querystring
  
  print '\nBEGIN REQUEST++++++++++++++++++++++++++++++++++++'
  print 'Request URL = ' + request_url
  r = requests.get(request_url)
  
  print '\nRESPONSE++++++++++++++++++++++++++++++++++++'
  print 'Response code: %d\n' % r.status_code
  print r.text
  
subject: Add signature.py from amazon's website