Issue when using array slicing

Question

I am an intermediate Python programmer. In my experiment, I use Linux command that outputs some results something like this:

OFPST_TABLE reply (xid=0x2):
  table 0 ("classifier"):
    active=1, lookup=41, matched=4
    max_entries=1000000
    matching:
      in_port: exact match or wildcard
      eth_src: exact match or wildcard
      eth_dst: exact match or wildcard
      eth_type: exact match or wildcard
      vlan_vid: exact match or wildcard
      vlan_pcp: exact match or wildcard
      ip_src: exact match or wildcard
      ip_dst: exact match or wildcard
      nw_proto: exact match or wildcard
      nw_tos: exact match or wildcard
      tcp_src: exact match or wildcard
      tcp_dst: exact match or wildcard

My goal is to collect the value of parameter active= which is variable from time to time (In this case it is just 1). I use the following slicing but it does not work:

string = sw.cmd('ovs-ofctl dump-tables ' + sw.name) # trigger the sh command 
count = count + int(string[string.rfind("=") + 1:])

I think I am using slicing wrong here but I tried many ways but I still get nothing. Can someone help me to extract the value of active= parameter from this string?

Thank you very much :)

Billy · Accepted Answer · 2016-12-13 16:37:19Z

2

How about regex?

import re
count +=  int(re.search(r'active\s*=\s*([^,])\s*,', string).group(1))

answered Dec 13, 2016 at 16:37

Billy

5,6592 gold badges31 silver badges57 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Andrey · Accepted Answer · 2016-12-13 16:37:41Z

2

1) Use regular expressions:

import re
m = re.search('active=(\d+)', '    active=1, lookup=41, matched=4')
print m.group(1)

2) str.rfind returns the highest index in the string where substring is found, it will find the rightmost = (of matched=4), that is not what you want.

3) Simple slicing won't help you because you need to know the length of the active value, overall it is not the best tool for this task.

answered Dec 13, 2016 at 16:37

Andrey

60.3k12 gold badges127 silver badges169 bronze badges

1 Comment

A_D Over a year ago

Thank you for clarification.

Collectives™ on Stack Overflow

Issue when using array slicing

2 Answers 2

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related