I have an IP-Range 192.0.0.2-4 as string and want to split it in two new strings
ip_start = '192.0.0.2'
ip_end = '192.0.0.4'
so I have to search for "-" in "192.0.0.2-4" and split there, but how can I make the second string?
-
can you post the string that you want to split?Julien Spronck– Julien Spronck2015-05-04 14:32:23 +00:00Commented May 4, 2015 at 14:32
-
1@JulienSpronck: it's there in the first sentence.Martijn Pieters– Martijn Pieters2015-05-04 14:33:05 +00:00Commented May 4, 2015 at 14:33
-
1Is the range always limited to the last byte of the address?Martijn Pieters– Martijn Pieters2015-05-04 14:33:22 +00:00Commented May 4, 2015 at 14:33
-
@MartijnPieters yes it is always limited to the last byteLoretta– Loretta2015-05-04 15:14:16 +00:00Commented May 4, 2015 at 15:14
Add a comment
|
3 Answers
If the range is always limited to the last byte (octet) of the address, split on the last dot of the address and replace it with your end value:
ip_start, _, end_value = iprange.partition('-')
first_three = ip_start.rpartition('.')[0]
ip_end = '{}.{}'.format(first_three, end_value)
I used str.partition() and str.rpartition() here as you only need to split just once; the methods are a little faster for that case. The methods return 3 strings, always; everything before the partition string, the partition string itself, and everything after. As we only need the first string of the . partition, I used indexing there to select it for assignment.
Since you don't need to keep that dash or dot I assigned those to a variable named _; that's just a convention and is used to signal that you'll ignore that value altogether.
Demo:
>>> iprange = '192.0.0.2-4'
>>> iprange.partition('-')
('192.0.0.2', '-', '4')
>>> iprange.partition('-')[0].rpartition('.')
('192.0.0', '.', '2')
>>> ip_start, _, end_value = iprange.partition('-')
>>> first_three = ip_start.rpartition('.')[0]
>>> ip_end = '{}.{}'.format(first_three, end_value)
>>> ip_start
'192.0.0.2'
>>> ip_end
'192.0.0.4'
For completeness sake: you can also use the str.rsplit() method to split a string from the right, but you need to include a limit in that case:
>>> first.rsplit('.', 1)
['192.0.0', '2']
Here the second argument, 1, limits the split to the first . dot found.
answered May 4, 2015 at 14:35
Martijn Pieters
1.1m326 gold badges4.2k silver badges3.4k bronze badges
Comments
You could build up the second string by using the piece from the "first" IP address.
>>> def getIPsFromClassCRange(ip_range):
... # first split up the string like you did
... tmp = ip_range.split("-")
... # get the fix part of the IP address
... classC = tmp[0].rsplit(".", 1)[0]
... # append the ending IP address
... tmp[1] = "%s.%s" % (classC, tmp[1])
... # return start and end ip as a useful tuple
... return (tmp[0], tmp[1])
...
>>> getIPsFromClassCRange("192.0.0.2-4")
('192.0.0.2', '192.0.0.4')
Comments
Here is 3 steps solution, using a generator expression :
def ip_bounds(ip_string):
"""Splits ip address range like '192.0.0.2-4'
into two ip addresses : '192.0.0.2','192.0.0.4'"""
# split ip address with last '.'
ip_head, ip_tail = ip_string.rsplit('.', 1)
# split last part with '-'
ip_values = ip_tail.split('-')
# create an ip address for each value
return tuple('{}.{}'.format(ip_head,i) for i in ip_values)
ip_start, ip_end = ip_bounds('192.0.0.2-4')
assert ip_start == '192.0.0.2'
assert ip_end == '192.0.0.4'
1 Comment
Jon Egeland
Please add some explanation to your answer so we can better understand what it does and how it works.