[BangPypers] Python List Comprehension Question
Bhargav Kowshik
bhargav.kowshik at yahoo.com
Fri Oct 3 18:09:31 CEST 2014
Thank you Kracekumar.
http://docs.python-guide.org/en/latest/writing/gotchas/#what-you-wrote"Python’s default arguments are evaluated once when the function is defined,not each time the function is called." Thank you,
Bhargav.
On Friday, October 3, 2014 9:18 PM, kracekumar ramaraju <kracethekingmaker at gmail.com> wrote:
On Fri, Oct 3, 2014 at 9:04 PM, Bhargav Kowshik <bhargav.kowshik at yahoo.com.dmarc.invalid> wrote:
Nice! Thank you very much Anand.But, I still don't know what is happening.Please point me to a resource to understand what is happening.
A common beginner mistake. More of such gotcha can be found here http://docs.python-guide.org/en/latest/writing/gotchas/ .
** Program **
def flat_it(values, result=list()):
for v in values:
if isinstance(v, list):
flat_it(v, result)
else:
result.append(v)
return result
x = [[1, 2, [3, 7]], 4]
print('Input: {0}'.format(x))
print('Output 1: {0}'.format(flat_it(x)))
print('Output 2: {0}'.format(flat_it(x)))
print('Output 3: {0}'.format(flat_it(x, list())))
** Output **
Input: [[1, 2, [3, 7]], 4]
Output 1: [1, 2, 3, 7, 4]
Output 2: [1, 2, 3, 7, 4, 1, 2, 3, 7, 4]
Output 3: [1, 2, 3, 7, 4]
Thank you,
Bhargav.
On Friday, October 3, 2014 8:48 PM, Anand Chitipothu <anandology at gmail.com> wrote:
On Fri, Oct 3, 2014 at 8:26 PM, Bhargav Kowshik <bhargav.kowshik at yahoo.com.dmarc.invalid> wrote:
We could use what Anand talked about at Pycon India about handling the headers in first row of a CSV.In this scenario, instead of default for result being None and checking if None everytime, we could have the default value an empty list.
def flat_it(values, result=list()):
for v in values:
if isinstance(v, list):
flat_it(v, result)
else:
result.append(v)
return result
x = [[1, 2, [3, 4, 5, 6, 7]], 4]
print x
print flat_it(x)
Thats a pitfall! Try calling flat_it once again and see what you get.
Anand
_______________________________________________
BangPypers mailing list
BangPypers at python.org
https://mail.python.org/mailman/listinfo/bangpypers
--
Thanks & Regards
kracekumar"Talk is cheap, show me the code" -- Linus Torvaldshttp://kracekumar.com
More information about the BangPypers
mailing list