import base64
import hashlib
import hmac
import json
import time
import urllib.request

endpoint = 'ep.api.iij.jp'
api_version = '20190625'
api_name = 'api_version'
http_method = 'GET'
access_key = b'YOUR ACCESS KEY HERE'
secret_key = b'YOUR SECRET KEY HERE'
signature_version = '2'
signature_method = 'HmacSHA256'
content_type = ''
expire = time.strftime('%FT%H:%M:%SZ', time.gmtime(time.time() + 12 * 60 * 60))


# make signature
path = '/r/{}/{}.json'.format(api_version, api_name)
 
header_strings = content_type + '\n'
header_strings += 'x-iijapi-expire' + ':' + expire + '\n'
header_strings += 'x-iijapi-signaturemethod' + ':' + signature_method + '\n'
header_strings += 'x-iijapi-signatureversion' + ':' + signature_version

string_to_sign = '\n'.join([http_method.upper(), '', header_strings, path])
signature = hmac.new(secret_key, string_to_sign.encode('utf-8'), hashlib.sha256).digest()
signature = base64.b64encode(signature)

# make request
headers = {
    'Authorization': b'IIJAPI ' + access_key + b':' + signature,
    'Content-Type': content_type,
    'x-iijapi-Expire': expire,
    'x-iijapi-SignatureMethod': signature_method,
    'x-iijapi-SignatureVersion': signature_version,
}

https_handler = urllib.request.HTTPSHandler()
opener = urllib.request.build_opener(https_handler)
urllib.request.install_opener(opener)

url = 'https://{}{}'.format(endpoint, path)

# call EP-API
request = urllib.request.Request(url, headers=headers)

# must use TLS 1.2 or higher
if hasattr(ssl, 'PROTOCOL_TLS'):
    context = ssl.SSLContext(ssl.PROTOCOL_TLS)
    context.options |= ssl.OP_NO_TLSv1
    context.options |= ssl.OP_NO_TLSv1_1
else:
    context = ssl.SSLContext(ssl.PROTOCOL_TLSv1_2)

print(json.load(response))

$ python ep-api.py
{'APIResult': {'RequestId': 'f9ba8be1-52dfb362-976062fa-0000db9f-d7d7668c', 'APIVersions': ['20190625']}}