why i have the output of [None, None, None]

Thu Apr 10 14:00:58 EDT 2014

On 4/10/2014 9:54 AM, length power wrote:
> >>> x=['','x1','x2','x3',' ']
> >>> x
> ['', 'x1', 'x2', 'x3', ' ']
> >>> [print("ok") for it in x if it.strip() !=""]

Don't use comprehensions for side effects. To get what you want, just 
write normal code.
for it in x:
 if it.strip() != '':
 print('ok')
> ok
> ok
> ok
> [None, None, None]
>> i understand there are three 'ok' in the output,but why i have the
> output of [None, None, None]

Reread the ref manual section on comprehensions.
-- 
Terry Jan Reedy