Suggestions for syrusakbary#4 (returning None) and syrusakbary#2 (log…

…ging server responses)

* removed unused "import socket"
* changed broad "except" clause to more specific "except ImportError"
* general PEP8 reformat
* added "debug" option for logging server responses/errors
* return None instead of True/False on several errors that may be temporary

validate_email.py

@@ -19,14 +19,17 @@
 
 import re
 import smtplib
-import socket
+import logging
 
 try:
     import DNS
     ServerError = DNS.ServerError
-except:
+except ImportError:
     DNS = None
-    class ServerError(Exception): pass
+
+    class ServerError(Exception):
+        pass
+
 # All we are really doing is comparing the input string to one
 # gigantic regular expression.  But building that regexp, and
 # ensuring its correctness, is made much easier by assembling it
@@ -45,58 +48,65 @@ class ServerError(Exception): pass
 NO_WS_CTL = r'\x01-\x08\x0b\x0c\x0f-\x1f\x7f'        # see 3.2.1. Primitive Tokens
 QUOTED_PAIR = r'(?:\\.)'                             # see 3.2.2. Quoted characters
 FWS = r'(?:(?:' + WSP + r'*' + CRLF + r')?' + \
-            WSP + r'+)'                                    # see 3.2.3. Folding white space and comments
+      WSP + r'+)'                                    # see 3.2.3. Folding white space and comments
 CTEXT = r'[' + NO_WS_CTL + \
-                r'\x21-\x27\x2a-\x5b\x5d-\x7e]'              # see 3.2.3
+        r'\x21-\x27\x2a-\x5b\x5d-\x7e]'              # see 3.2.3
 CCONTENT = r'(?:' + CTEXT + r'|' + \
-                     QUOTED_PAIR + r')'                        # see 3.2.3 (NB: The RFC includes COMMENT here
-                                                                                                         # as well, but that would be circular.)
+           QUOTED_PAIR + r')'                        # see 3.2.3 (NB: The RFC includes COMMENT here
+# as well, but that would be circular.)
 COMMENT = r'\((?:' + FWS + r'?' + CCONTENT + \
-                    r')*' + FWS + r'?\)'                       # see 3.2.3
+          r')*' + FWS + r'?\)'                       # see 3.2.3
 CFWS = r'(?:' + FWS + r'?' + COMMENT + ')*(?:' + \
-             FWS + '?' + COMMENT + '|' + FWS + ')'         # see 3.2.3
+       FWS + '?' + COMMENT + '|' + FWS + ')'         # see 3.2.3
 ATEXT = r'[\w!#$%&\'\*\+\-/=\?\^`\{\|\}~]'           # see 3.2.4. Atom
 ATOM = CFWS + r'?' + ATEXT + r'+' + CFWS + r'?'      # see 3.2.4
 DOT_ATOM_TEXT = ATEXT + r'+(?:\.' + ATEXT + r'+)*'   # see 3.2.4
 DOT_ATOM = CFWS + r'?' + DOT_ATOM_TEXT + CFWS + r'?' # see 3.2.4
 QTEXT = r'[' + NO_WS_CTL + \
-                r'\x21\x23-\x5b\x5d-\x7e]'                   # see 3.2.5. Quoted strings
+        r'\x21\x23-\x5b\x5d-\x7e]'                   # see 3.2.5. Quoted strings
 QCONTENT = r'(?:' + QTEXT + r'|' + \
-                     QUOTED_PAIR + r')'                        # see 3.2.5
+           QUOTED_PAIR + r')'                        # see 3.2.5
 QUOTED_STRING = CFWS + r'?' + r'"(?:' + FWS + \
-                                r'?' + QCONTENT + r')*' + FWS + \
-                                r'?' + r'"' + CFWS + r'?'
+                r'?' + QCONTENT + r')*' + FWS + \
+                r'?' + r'"' + CFWS + r'?'
 LOCAL_PART = r'(?:' + DOT_ATOM + r'|' + \
-                         QUOTED_STRING + r')'                    # see 3.4.1. Addr-spec specification
+             QUOTED_STRING + r')'                    # see 3.4.1. Addr-spec specification
 DTEXT = r'[' + NO_WS_CTL + r'\x21-\x5a\x5e-\x7e]'    # see 3.4.1
 DCONTENT = r'(?:' + DTEXT + r'|' + \
-                     QUOTED_PAIR + r')'                        # see 3.4.1
+           QUOTED_PAIR + r')'                        # see 3.4.1
 DOMAIN_LITERAL = CFWS + r'?' + r'\[' + \
-                                 r'(?:' + FWS + r'?' + DCONTENT + \
-                                 r')*' + FWS + r'?\]' + CFWS + r'?'  # see 3.4.1
+                 r'(?:' + FWS + r'?' + DCONTENT + \
+                 r')*' + FWS + r'?\]' + CFWS + r'?'  # see 3.4.1
 DOMAIN = r'(?:' + DOT_ATOM + r'|' + \
-                 DOMAIN_LITERAL + r')'                       # see 3.4.1
+         DOMAIN_LITERAL + r')'                       # see 3.4.1
 ADDR_SPEC = LOCAL_PART + r'@' + DOMAIN               # see 3.4.1
 
 # A valid address will match exactly the 3.4.1 addr-spec.
 VALID_ADDRESS_REGEXP = '^' + ADDR_SPEC + '$'
 
-def validate_email(email, check_mx=False,verify=False):
 
+def validate_email(email, check_mx=False, verify=False, debug=False):
     """Indicate whether the given string is a valid email address
     according to the 'addr-spec' portion of RFC 2822 (see section
     3.4.1).  Parts of the spec that are marked obsolete are *not*
     included in this test, and certain arcane constructions that
     depend on circular definitions in the spec may not pass, but in
     general this should correctly identify any email address likely
     to be in use as of 2011."""
+    if debug:
+        logger = logging.getLogger('validate_email')
+    else:
+        logger = None
+
     try:
         assert re.match(VALID_ADDRESS_REGEXP, email) is not None
         check_mx |= verify
         if check_mx:
-            if not DNS: raise Exception('For check the mx records or check if the email exists you must have installed pyDNS python package')
+            if not DNS:
+                raise Exception('For check the mx records or check if the email exists you must '
+                                'have installed pyDNS python package')
             DNS.DiscoverNameServers()
-            hostname = email[email.find('@')+1:]
+            hostname = email[email.find('@') + 1:]
             mx_hosts = DNS.mxlookup(hostname)
             for mx in mx_hosts:
                 try:
@@ -108,20 +118,30 @@ def validate_email(email, check_mx=False,verify=False):
                     status, _ = smtp.helo()
                     if status != 250:
                         smtp.quit()
+                        if debug:
+                            logger.debug(u'%s answer: %s - %s', mx[1], status, _)
                         continue
                     smtp.mail('')
                     status, _ = smtp.rcpt(email)
-                    if status != 250:
+                    if status == 250:
                         smtp.quit()
-                        return False
+                        return True
+                    if debug:
+                        logger.debug(u'%s answer: %s - %s', mx[1], status, _)
                     smtp.quit()
-                    break
-                except smtplib.SMTPServerDisconnected: #Server not permits verify user
-                    break
+                except smtplib.SMTPServerDisconnected:  # Server not permits verify user
+                    if debug:
+                        logger.debug(u'%s disconected.', mx[1])
                 except smtplib.SMTPConnectError:
-                    continue
-    except (AssertionError, ServerError): 
+                    if debug:
+                        logger.debug(u'Unable to connect to %s.', mx[1])
+            return None
+    except AssertionError:
         return False
+    except ServerError:
+        if debug:
+            logger.debug(u'ServerError exception raised.')
+        return None
     return True
 
 # import sys