--- a/units_cur
+++ b/units_cur
@@ -28,8 +28,12 @@
 #
 #
 
-version = '5.0'
+version = '5.1'
 
+# Version 5.1:
+#
+# Switch to urllib to avoid requests dependency.
+#
 # Version 5.0:
 #
 # Rewrite to support multiple different data sources due to disappearance
@@ -54,9 +58,11 @@
 # Python 2 or Python 3.  Thanks to Ray Hamel for some help with this update.  
 
 # Normal imports
-import requests
 import codecs
 import json
+import urllib.error
+import urllib.parse
+import urllib.request
 from argparse import ArgumentParser
 from collections import OrderedDict
 from datetime import date
@@ -303,11 +309,12 @@
                                                   currency[code][rate_index]))
 
 def getjson(address,args=None):
+  if args:
+    address = address + "?" + urllib.parse.urlencode(args)
   try:
-    res = requests.get(address,args)
-    res.raise_for_status()
-    return(res.json())
-  except requests.exceptions.RequestException as e:
+    res = urllib.request.urlopen(address)
+    return(json.load(res))
+  except urllib.error.URLError as e:
     stderr.write('Error connecting to currency server:\n{}.\n'.format(e))
     exit(1)
         
@@ -337,14 +344,8 @@
   if verbose and base!='EUR':
     stderr.write('European bank uses euro for base currency.  Specified base {} ignored.\n'.format(base))
   import xml.etree.ElementTree as ET
-  try:
-    res=requests.get('https://www.ecb.europa.eu/stats/eurofxref/eurofxref-daily.xml')
-    res.raise_for_status()
-    data = ET.fromstring(res.content)[2][0]
-  except requests.exceptions.RequestException as e:
-    stderr.write('Error connecting to currency server:\n{}.\n'.
-                 format(e))
-    exit(1)
+  res=urllib.request.urlopen('https://www.ecb.europa.eu/stats/eurofxref/eurofxref-daily.xml')
+  data = ET.fromstring(res.read())[2][0]
   for entry in data.iter():
     if entry.get('time'):
       continue
@@ -596,7 +597,6 @@
     docpi=True
   
 if docpi:
-  headers = {'Content-type': 'application/json'}
   yearlist = list(range(date.today().year,1912,-10))
   if yearlist[-1]>1912:
     yearlist.append(1912)
@@ -605,29 +605,18 @@
   query = {"seriesid": ['CUUR0000SA0']}
   if cpikey:
     query["registrationkey"]=cpikey
-  ########################################################################
-  # The api.bls.gov site currently (2024-02-15) resolves to an
-  # IPv4 address which works, and an IPv6 address which does
-  # not.  The urllib3 package does not currently implement the
-  # Happy Eyeballs algorithm, nor any other mechanism to re-try
-  # hung connections with alternative addresses returned by DNS.
-  # In the interest of expediency, we temporarily force the
-  # connection to api.bls.gov to only use IPv4; hopefully at
-  # some future date either urllib3 will gain the necessary
-  # features and/or the BLS will fix their configuration so
-  # that all A and AAAA records for api.bls.gov resolve to an
-  # operational server.  At that time we can remove the three
-  # references to "requests.packages.urllib3.util.connection.HAS_IPV6"
-  # in this function.
-  ########################################################################
-  save_rpuucH = requests.packages.urllib3.util.connection.HAS_IPV6
-  requests.packages.urllib3.util.connection.HAS_IPV6 = False
   for endyear in range(len(yearlist)-1):
     query["startyear"]=str(yearlist[endyear+1]+1)
     query["endyear"]=str(yearlist[endyear])
     data = json.dumps(query)
-    p = requests.post('https://api.bls.gov/publicAPI/v2/timeseries/data/', data=data, headers=headers)
-    json_data = json.loads(p.text)
+    p = urllib.request.urlopen(
+            urllib.request.Request(
+                'https://api.bls.gov/publicAPI/v2/timeseries/data/',
+                data=json.dumps(query),
+                headers={'Content-type': 'application/json'}
+            )
+        )
+    json_data = json.load(p)
     if json_data['status']=="REQUEST_NOT_PROCESSED":
       docpi=False
       stderr.write("Unable to update CPI data: Exceeded daily threshold for BLS requests\n")
@@ -644,7 +633,6 @@
               lastyear=year
             firstcpi=value
             firstyear=year
-  requests.packages.urllib3.util.connection.HAS_IPV6 = save_rpuucH              
 if docpi:   # Check again because request may have failed
   cpi.reverse()
   cpistr = '\n'.join(cpi)