Re: Learning Python via a little word frequency program
import collections
names = "freddy fred bill jock kevin andrew kevin kevin jock"
freq = collections.defaultdict(int)
for name in names.split():
freq[name] += 1
keys = freq.keys()
keys.sort(key = freq.get, reverse = True)
for k in keys:
print "%-10s: %d" % (k, freq[k])
On Jan 9, 6:58 pm, Andrew Savige <[EMAIL PROTECTED]> wrote:
> I'm learning Python by reading David Beazley's "Python Essential Reference"
> book and writing a few toy programs. To get a feel for hashes and sorting,
> I set myself this little problem today (not homework, BTW):
>
> Given a string containing a space-separated list of names:
>
> names = "freddy fred bill jock kevin andrew kevin kevin jock"
>
> produce a frequency table of names, sorted descending by frequency.
> then ascending by name. For the above data, the output should be:
>
> kevin : 3
> jock : 2
> andrew: 1
> bill : 1
> fred : 1
> freddy: 1
>
> Here's my first attempt:
>
> names = "freddy fred bill jock kevin andrew kevin kevin jock"
> freq = {}
> for name in names.split():
> freq[name] = 1 + freq.get(name, 0)
> deco = zip([-x for x in freq.values()], freq.keys())
> deco.sort()
> for v, k in deco:
> print "%-10s: %d" % (k, -v)
>
> I'm interested to learn how more experienced Python folks would solve
> this little problem. Though I've read about the DSU Python sorting idiom,
> I'm not sure I've strictly applied it above ... and the -x hack above to
> achieve a descending sort feels a bit odd to me, though I couldn't think
> of a better way to do it.
>
> I also have a few specific questions. Instead of:
>
> for name in names.split():
> freq[name] = 1 + freq.get(name, 0)
>
> I might try:
>
> for name in names.split():
> try:
> freq[name] += 1
> except KeyError:
> freq[name] = 1
>
> Which is preferred?
>
> Ditto for:
>
> deco = zip([-x for x in freq.values()], freq.keys())
>
> versus:
>
> deco = zip(map(operator.neg, freq.values()), freq.keys())
>
> Finally, I might replace:
>
> for v, k in deco:
> print "%-10s: %d" % (k, -v)
>
> with:
>
> print "\n".join("%-10s: %d" % (k, -v) for v, k in deco)
>
> Any feedback on good Python style, performance tips, good books
> to read, etc. is appreciated.
>
> Thanks,
> /-\
>
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Re: How to sort very large arrays?
On Jun 14, 1:54 am, kj <[EMAIL PROTECTED]> wrote:
> I'm downloading some very large tables from a remote site. I want
> to sort these tables in a particular way before saving them to
> disk. In the past I found that the most efficient way to do this
> was to piggy-back on Unix's highly optimized sort command. So,
> from within a Perl script, I'd create a pipe handle through sort
> and then just print the data through that handle:
This is a python clone of your code from a python rookie :)
from os import popen
p = popen("sort -t '\t' -k1,1 -k2,2 -u > %s" % out_file)
for line in data:
print >> p, line
there is no "die $!" here, I think it is good to let python
throw the exception to your console
>
> open my $out, "|$sort -t '\t' -k1,1 -k2,2 -u > $out_file" or die $!;
> print $out $_ for @data;
>
> But that's distinctly Perlish, and I'm wondering what's the "Python
> Way" to do this.
>
> TIA!
>
> kynn
>
> --
> NOTE: In my address everything before the first period is backwards;
> and the last period, and everything after it, should be discarded.
--
http://mail.python.org/mailman/listinfo/python-list
Re: How to sort very large arrays?
On Jun 14, 1:54 am, kj <[EMAIL PROTECTED]> wrote:
> I'm downloading some very large tables from a remote site. I want
> to sort these tables in a particular way before saving them to
> disk. In the past I found that the most efficient way to do this
> was to piggy-back on Unix's highly optimized sort command. So,
> from within a Perl script, I'd create a pipe handle through sort
> and then just print the data through that handle:
This is a python clone of your code from a python rookie :)
from os import popen
p = popen("sort -t '\t' -k1,1 -k2,2 -u > %s" % out_file)
for line in data:
print >> p, line
there is no "die $!" here, I think it is good to let python
throw the exception to your console
>
> open my $out, "|$sort -t '\t' -k1,1 -k2,2 -u > $out_file" or die $!;
> print $out $_ for @data;
>
> But that's distinctly Perlish, and I'm wondering what's the "Python
> Way" to do this.
>
> TIA!
>
> kynn
>
> --
> NOTE: In my address everything before the first period is backwards;
> and the last period, and everything after it, should be discarded.
--
http://mail.python.org/mailman/listinfo/python-list
