diff --git a/pyfbx/__main__.py b/pyfbx/__main__.py
index 362e0ad..fa1a366 100644
--- a/pyfbx/__main__.py
+++ b/pyfbx/__main__.py
@@ -43,13 +43,13 @@ def main():
                 with open(args.token[2:]) as tok_file:
                     token = tok_file.read().strip()
         else:
-            log.warning(f"Registering app {__name__}, id {args.app_id}, Press button")
+            log.warning("Registering app {}, id {}, Press button".format(__name__, args.app_id))
             token = myfb.register(app_id=args.app_id, app_name=__name__,
                                   device=os.uname().nodename)
-            log.warning(f"Save your application token: {token}")
+            log.warning("Save your application token: {}".format(token))
         myfb.mksession(app_id=args.app_id, token=token)
         pp = pprint.PrettyPrinter(indent=4)
-        pp.pprint(eval(f"myfb.{args.command}"))
+        pp.pprint(eval("myfb.{}".format(args.command)))
         return 0
     except BaseException as err:
         print(err)
diff --git a/pyfbx/client.py b/pyfbx/client.py
index a9ecf3f..ec52b9c 100644
--- a/pyfbx/client.py
+++ b/pyfbx/client.py
@@ -66,14 +66,14 @@ class FbxTransport():
         response = req_response.json()
         if response['success']:
             if 'result' in response:
-                self.log.debug(f"<< Got  {response['result']}")
+                self.log.debug("<< Got  {}".format(response['result']))
                 return response['result']
         else:
             raise FbxErrorResponse(response['error_code'], response['msg'])
 
     def get_local_base(self, url=api._DISC_HTTP_URL):
-        response = self._session.get(f"{url}/api_version").json()
-        self.log.debug(f"<< Detected api {response['api_version']}")
+        response = self._session.get("{}/api_version".format(url)).json()
+        self.log.debug("<< Detected api {}".format(response['api_version']))
         return "%s%sv%s" % (url, response['api_base_url'],
                             response['api_version'][0])
 
@@ -105,10 +105,10 @@ class Fbx():
         s = "pending"
         self.log.info("Press Ok on the freebox to register application")
         while s == "pending":
-            s = self._trn.api_exec("GET", f"login/authorize/{trackid}")["status"]
+            s = self._trn.api_exec("GET", "login/authorize/{}".format(trackid))["status"]
             if s == "pending":
                 time.sleep(1)
-        self.log.debug(f"Registration returned: {s}")
+        self.log.debug("Registration returned: {}".format(s))
         return s == "granted" and self.token
 
     def mksession(self, app_id=None, token=None):
@@ -128,7 +128,7 @@ class Fbx():
             session_token = resp["session_token"]
             self.app_id = app_id
             self._trn.set_session_header(session_token)
-            self.log.info(f"Authenticated")
+            self.log.info("Authenticated".format())
             return resp["permissions"]
 
 
@@ -138,13 +138,13 @@ class FbxErrorResponse(Exception):
         self.msg = msg
 
     def __str__(self):
-        return f'{self.msg} [{self.error_code}]'
+        return '{} [{}]'.format(self.msg, self.error_code)
 
 
 log = logging.getLogger("pyfbx")
 
 # All FB subsystems are classes deriving from FbxClass
 for _classname in api.SYSTEMS:
-    log.debug(f"Adding class {_classname} to locals")
+    log.debug("Adding class {} to locals".format(_classname))
     locals()[_classname] = type(_classname, (FbxClass, ), {})
     __all__.append(_classname)
diff --git a/pyfbx/mdns.py b/pyfbx/mdns.py
index c51de2f..cd3cd2d 100644
--- a/pyfbx/mdns.py
+++ b/pyfbx/mdns.py
@@ -45,9 +45,9 @@ class FbxMDNS():
             prop = self.svc_prop
             base = "%sv%s" % (prop['api_base_url'], prop['api_version'][0])
             if int(prop['https_available']):
-                return f"https://{prop['api_domain']}:{prop['https_port']}{base}"
+                return "https://{}:{}{}".format(prop['api_domain'], prop['https_port'], base)
             else:
-                return f"http://{prop['api_domain']}{base}"
+                return "http://{}{}".format(prop['api_domain'], base)
 
     @property
     def svc_info(self):
diff --git a/pyfbx/utils.py b/pyfbx/utils.py
index 71900b3..033d9ea 100644
--- a/pyfbx/utils.py
+++ b/pyfbx/utils.py
@@ -37,11 +37,11 @@ def add_class_func(cls, name, method):
 
     params = (["post_data"] if method.args else []) + get_params(method.endpoint)
     input_params = ", ".join(params)
-    passed_param = ", ".join([f"{e}={e}" for e in params])
+    passed_param = ", ".join(["{}={}".format(e, e) for e in params])
     namespace = {}
-    code = (f"def func(self, {input_params}):\n"
-            f"    return self._trn.api_exec(\n"
-            f"        \"{method.http_method}\", \"{method.endpoint}\", {passed_param})")
+    code = ("def func(self, {}):\n"
+            "    return self._trn.api_exec(\n"
+            "        \"{}\", \"{}\", {})".format(input_params, method.http_method, method.endpoint, passed_param))
     exec(code, namespace)
     func = namespace['func']
     func.__name__ = name