Home Original page

My Big Dict.

John Hunter jdhunter at ace.bsd.uchicago.edu
Wed Jul 2 08:12:52 EDT 2003 
>>>>> "Russell" == Russell Reagan <rreagan at attbi.com> writes:

    drs> f = open('somefile.txt')
    drs> d = {}
    drs> l = f.readlines()
    drs> for i in l:
    drs>     a,b = i.split('!')
    drs>     d[a] = b.strip()


I would make one minor modification of this.  If the file were *really
long*, you could run into troubles trying to hold it in memory.  I
find the following a little cleaner (with python 2.2), and doesn't
require putting the whole file in memory.  A file instance is an
iterator (http://www.python.org/doc/2.2.1/whatsnew/node4.html) which
will call readline as needed:

     d = {}
     for line in file('sometext.dat'):
         key,val = line.split('!')
         d[key] = val.strip()

Or if you are not worried about putting it in memory, you can use list
comprehensions for speed

  d = dict([ line.split('!') for line in file('somefile.text')])

    Russell> I have just started learning Python, and I have never
    Russell> used dictionaries in Python, and despite the fact that
    Russell> you used mostly non-descriptive variable names, I can
    Russell> still read your code perfectly and know exactly what it
    Russell> does. I think I could use dictionaries now, just from
    Russell> looking at your code snippet.  Python rules :-)

Truly.

JDH
More information about the Python-list mailing list