Hi guys,
I am reading and doing examples from Python Web Programming and
Have a question about the dictionary:
counter = {}
file = open("d:\myfile.txt") # the time has come the walrus said
while 1:
line = file.readline()
if line == "":
break
for w in line.split():
if counter.has_key(w):
counter[w] += 1
else:
counter[w] = 1
file.close()
words = counter.keys()
words.sort()
wor w in words:
print w, counter{w}
Output is:
Come 1
Has 1
Said 1
The 2
Time 1
Walaus 1
????
Okay, I understand counter is set up as a dictionary and a dictionary
has a key and a value.
How does the dictionary get built? I'm not following the logic in how
the key, the actual word, is having a value assigned.
Thanks,
SteveO
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of Kent Johnson
Sent: Friday, December 22, 2006 10:38 AM
To: Carlos
Cc: tutor@python.org
Subject: Re: [Tutor] Lists on the fly?
Carlos wrote:
> Hello,
>
> I am wondering if it is possible to create lists on the fly. The
> script that I'm working on needs a number of parameters, one of those
> is population, and this corresponds to the number of solutions that a
> genetic algorithm generates on each generation (iteration). The thing
> is that I need to generate one list for each population member and
> then append the corresponding population members to that particular
list.
>
> This is only so you can have an idea:
>
> for i in range(5):
> 'list_%i' % (i) = []
>
> or:
>
> for i in range(5):
> lista_+'%i' % (i) = []
>
> :-[
>
> Is this possible?
It is possible, using exec, but it is not the right solution to your
problem. You want a bunch of lists each associated with a name. The way
to do this is put the lists in a dict; the name is the key, the list is
the value. Your example would look like this:
lists = {}
for i in range(5):
lists['list_%i' % (i)] = []
Kent
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http://mail.python.org/mailman/listinfo/tutor
