Re: Appending to dictionary of lists
Alex van der Spek zd...@xs4all.nl writes: refd=dict.fromkeys(csvr.fieldnames,[]) ... I do not understand why this appends v to every key k each time. You have initialized every element of refd to the same list. Try refd = dict((k,[]) for k in csvr.fieldnames) instead. -- http://mail.python.org/mailman/listinfo/python-list
Re: Appending to dictionary of lists
On Tue, May 3, 2011 at 12:56 PM, Paul Rubin no.email@nospam.invalid wrote:
Alex van der Spek zd...@xs4all.nl writes:
refd=dict.fromkeys(csvr.fieldnames,[]) ...
I do not understand why this appends v to every key k each time.
You have initialized every element of refd to the same list. Try
refd = dict((k,[]) for k in csvr.fieldnames)
instead.
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Agreed. Here's another way: using a dictionary comprehension - a feature in
2.7 and up:
#!/usr/local/cpython-2.7/bin/python
import csv
import pprint
csvf=open('foo.csv','rb')
csvr=csv.DictReader(csvf)
#refd=dict.fromkeys(csvr.fieldnames, [])
refd = { key: [] for key in csvr.fieldnames }
for row in csvr:
for (k,v) in row.items():
refd[k].append(v)
pprint.pprint(refd)
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Re: Appending to dictionary of lists
Thank you! Would never have found that by myself. Paul Rubin no.email@nospam.invalid wrote in message news:7x7ha75zib@ruckus.brouhaha.com... Alex van der Spek zd...@xs4all.nl writes: refd=dict.fromkeys(csvr.fieldnames,[]) ... I do not understand why this appends v to every key k each time. You have initialized every element of refd to the same list. Try refd = dict((k,[]) for k in csvr.fieldnames) instead. -- http://mail.python.org/mailman/listinfo/python-list
