check if a string matches an IP address pattern in python

Question

What is the fastest way to check if a string matches a certain pattern  Is regex the best way   For example  I have a bunch of strings and want to check each one to see if they are a valid IP address  valid in this case meaning correct format   is the fastest way to do this using regex  Or is there something faster with like string formatting or something    Something like this is what I have been doing so far   for st in strs      if re match   d 1 3    d 1 3    d 1 3    d 1 3    st     None         print  IP

User · Answer

I cheated and used combination of multiple answers submitted by other people  I think this is pretty clear and straight forward piece of code  ip validation should return True or False  Also this answer only works for IPv4 addresses  import re ip match   re match              join     d 1 3     4         ip input  ip validate   bool ip match  if ip validate      ip validate  amp   all map lambda n  0  lt   int n   lt   255  ip match groups

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I m normally the one of the very few Python experts who steadfastly defends regular expressions  they have quite a bad reputation in the Python community   but this is not one of those cases -- accepting  say   333 444 555 666  as an  IP address  is really bad  and if you need to do more checks after matching the RE  much of the point of using a RE is lost anyway   So  I second  Mark s recommendations heartily  IPy for generality and elegance  including support of IPv6 if you want    string operations and int checks if you only need IPv4  but  think twice about that limitation  and then think one more -- IPv6 s time has way come -    def isgoodipv4 s       pieces   s split          if len pieces     4  return False     try  return all 0 lt  int p  lt 256 for p in pieces      except ValueError  return False   I d far rather do that than a convoluted RE to match only numbers between 0 and 255 -

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On Python 3 6 I think is much simpler as ipaddress module is already included   import ipaddress      def is ipv4 string           try              ipaddress IPv4Network string              return True         except ValueError              return False

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Other regex answers in this page will accept an IP with a number over 255   This regex will avoid this problem   import re  def validate ip ip str       reg   r     0-9   1-9  0-9  1 0-9  2  2 0-4  0-9  25 0-5      3   0-9   1-9  0-9  1 0-9  2  2 0-4  0-9  25 0-5         if re match reg  ip str           return True     else          return False

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Your regular expression doesn t check for the end of the string  so it would match   123 45 67 89abc123boogabooga   To fix this  use     d 1 3    d 1 3    d 1 3    d 1 3       note the   at the end    Finally  in Python the usual style is to use is not None instead of    None

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This works for ipv6 addresses as well   Unfortunately it Works for python3 only  import ipaddress  def valid ip address       try           print ipaddress ip address address          return True     except          return False  print valid ip  10 10 20 30   print valid ip  2001 DB8  1   print valid ip  gibberish

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If you are validating IP address I would suggest the following   import socket  try      socket inet aton addr      return True except socket error      return False   If you just want to check if it is in the right format then you would want to do it for all legal bases  not just base 10 numbering    Also  are the IP address IPv4 only  and none are IPv6  then you could just look up what valid address are and use split    to get individual components of the IP  and int    to type-caste for comparison   A quick reference to valid IPv4 rules is here

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If you use Python3  you can use ipaddress module http   docs python org py3k library ipaddress html  Example     gt  gt  gt  import ipaddress   gt  gt  gt  ipv6    2001 0db8 0a0b 12f0 0000 0000 0000 0001   gt  gt  gt  ipv4    192 168 2 10   gt  gt  gt  ipv4invalid    266 255 9 10   gt  gt  gt  str    Tay Tay    gt  gt  gt  ipaddress ip address ipv6  IPv6Address  2001 db8 a0b 12f0  1     gt  gt  gt  ipaddress ip address ipv4  IPv4Address  192 168 2 10     gt  gt  gt  ipaddress ip address ipv4invalid  Traceback  most recent call last     File   lt console gt    line 1  in  lt module gt    File   usr lib python3 4 ipaddress py   line 54  in ip address     address  ValueError   266 255 9 10  does not appear to be an IPv4 or IPv6 address   gt  gt  gt  ipaddress ip address str  Traceback  most recent call last     File   lt console gt    line 1  in  lt module gt    File   usr lib python3 4 ipaddress py   line 54  in ip address     address  ValueError   Tay Tay  does not appear to be an IPv4 or IPv6 address

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You may try the following  the program can be further optimized    path     abc test1 txt  fh   open  path   r   ip arr tmp      ip arr      ip arr invalid       for lines in fh readlines        resp   re search     0-9      0-9      0-9      0-9      lines      print resp      if resp    None          p1 p2 p3 p4     resp group 1   resp group 2   resp group 3   resp group 4                  if  int p1   lt  0 or int p2   lt  0 or int p3   lt  0 or int p4   lt 0              ip arr invalid append   s  s  s  s    p1 p2 p3 p4           elif  int p1   gt  255 or int p2   gt  255 or int p3   gt  255 or int p4   gt  255               ip arr invalid append   s  s  s  s    p1 p2 p3 p4           elif  len p1  gt 3 or len p2  gt 3 or len p3  gt 3 or len p4  gt 3               ip arr invalid append   s  s  s  s    p1 p2 p3 p4           else             ip      s  s  s  s    p1 p2 p3 p4              ip arr tmp append ip   print ip arr tmp  for item in ip arr tmp      if not item in ip arr         ip arr append item   print ip arr

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usr bin python import sys def check ip address       part address split          temp True     if len part     4              temp False             return temp     for p in part              if not 0 lt   int p   lt   255                      temp False                     return temp             else                      temp True     return temp if   name       main         print check ip sys argv 1     Save the code with some name say- check ip py and run it as python check ip py 192 168 560 25 Note -  Above code fails for the below ip address- 023 65 029 33

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you should precompile the regexp  if you use it repeatedly  re ip   re compile   d 1 3    d 1 3    d 1 3    d 1 3       note the terminating   to really match only the IPs   then use  if re ip match st       print   IP    but   is e g   111 222 333 444  really the IP   i d look at netaddr or ipaddr libraries whether they can be used to match IPs

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We do not need any import to do this  This also works much faster  def is valid ip str ip addr              return  returns true if IP is valid  else returns False           ip blocks   str str ip addr  split         if len ip blocks     4         for block in ip blocks               Check if number is digit  if not checked before calling this function            if not block isdigit                   return False            tmp   int block             if 0  gt  tmp  gt  255                 return False        return True     return False

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One more validation without re   def validip ip       return ip count         3 and  all 0 lt  int num  lt 256 for num in ip rstrip   split        for i in   123 233 42 12   3234 23 453 353   -2 23 24 234   1 2 3 4        print i validip i

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Very simple to check whether given IP is valid or not using in built library ipaddress  You can also validate using mask value   ip    30 0 0 1     valid  ip    300 0 0 0 8    invalid  ip    30 0 0 0 8     valid  ip    30 0 0 1 8     invalid  ip    fc00 da00  3402 69b1   valid  ip    fc00 da00  3402 69b1 128   valid  ip    fc00 da00  3402 69b1 33333   invalid  if ip find       gt  0      try          temp2   ipaddress ip network ip          print  Valid IP network               except ValueError          print  Invalid IP network  value error   else              try          temp2   ipaddress ip address ip          print  Valid IP       except ValueError          print  Invalid IP     Note  Tested in Python 3 4 3

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Install netaddr package  sudo pip install netaddr   And then you can do this   gt  gt  gt  from netaddr import valid ipv4  gt  gt  gt  valid ipv4  11 1 1 2    True  gt  gt  gt  valid ipv4  11 1 1 a   False   Also you create a IPAddress object from that string and a lot more ip related operations   gt  gt  gt  from netaddr import IPAddress  gt  gt  gt  ip   IPAddress  11 1 1 1    gt  gt  gt   f for f in dir ip  if      not in f     module     set value     value    bin    bits    format    info    ipv4    ipv6    is hostmask    is ipv4 compat    is ipv4 mapped    is link local    is loopback    is multicast    is netmask    is private    is reserved    is unicast    key    netmask bits    packed    reverse dns    sort key    value    version    words

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You can make it a little faster by compiling it   expression   re compile    d 1 3    d 1 3    d 1 3    d 1 3     for st in strs      if expression match st          print  IP

User · Answer

update  The original answer bellow is good for 2011  but since 2012  one is likely better using Python s ipaddress stdlib module - besides checking IP validity for IPv4 and IPv6  it can do a lot of other things as well  lt  update gt   It looks like you are trying to validate IP addresses  A regular expression is probably not the best tool for this   If you want to accept all valid IP addresses  including some addresses that you probably didn t even know were valid  then you can use IPy  Source    from IPy import IP IP  127 0 0 1     If the IP address is invalid it will throw an exception   Or you could use socket  Source    import socket try      socket inet aton addr        legal except socket error        Not legal   If you really want to only match IPv4 with 4 decimal parts then you can split on dot and test that each part is an integer between 0 and 255   def validate ip s       a   s split          if len a     4          return False     for x in a          if not x isdigit                return False         i   int x          if i  lt  0 or i  gt  255              return False     return True   Note that your regular expression doesn t do this extra check  It would accept 999 999 999 999 as a valid address

[python] check if a string matches an IP address pattern in python?

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