Figure out if element is present in multi-dimensional array in python

Question

I am parsing a log containing nicknames and hostnames. I want to end up with an array that contains the hostname and the latest used nickname.

I have the following code, which only creates a list over the hostnames:

hostnames = []

# while(parsing):
#    nick = nick_on_current_line
#    host = host_on_current_line 

if host in hostnames:
    # Hostname is already present.
    pass
else:
    # Hostname is not present
    hostnames.append(host)

print hostnames
# ['[email protected]', '[email protected]', '[email protected]']

I thought it would be nice to end up with something along the lines of the following:

# [['[email protected]', 'John'], ['[email protected]', 'Mary'], ['[email protected]', 'Joe']]

My problem is finding out if the hostname is present in such a list

hostnames = []

# while(parsing):
#    nick = nick_on_current_line
#    host = host_on_current_line   

if host in hostnames[0]: # This doesn't work.
    # Hostname is already present.
    # Somehow check if the nick stored together 
    # with the hostname is the latest one
else:
    # Hostname is not present
    hostnames.append([host, nick])

Are there any easy fix to this, or should I try a different approach? I could always have an array with objects or structs (if there is such a thing in python), but I would prefer a solution to my array problem.

Mark Byers · Accepted Answer · 2010-05-01 20:48:25Z

4

Use a dictionary instead of a list. Use the hostname as the key and the username as the value.

answered May 1, 2010 at 20:48

Mark Byers

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1 Comment

PaulMcG Over a year ago

A dict will do all you need. Repeated updates for the same host will only keep the last value, and accessing dict.items() will give back the array of host->nick entries.

rcoyner · Accepted Answer · 2010-05-01 20:50:08Z

3

Just use a dictionary instead.

names = {}

while(parsing):
    nick = nick_on_current_line
    host = host_on_current_line   

    names[host] = nick

answered May 1, 2010 at 20:50

rcoyner

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1 Comment

Terje Over a year ago

Wow. A lot easier than I expected. Thanks.

kennytm · Accepted Answer · 2010-05-01 20:46:06Z

2

if host in zip(*hostnames)[0]:

or

if host in (x[0] for x in hostnames):

answered May 1, 2010 at 20:46

kennytm

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1 Comment

PaulMcG Over a year ago

Testing for membership in a set or dict is far more scaleable than testing within a list, especially for so nicely hashable an item as a hostname string.

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