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list.count does not appear to function
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list.count does not appear to function
#1
I am learning about lists and apparently list.count does not function in the following:
mylist = [5, 12, 27, 3, 12, 5, 9, 5, 11]
mylist.count(3)
print(mylist)
The output I get is
Output:
[5, 12, 27, 3, 12, 5, 9, 5, 11]
whereas it should return 1
When I use .insert, .reverse, .extend all is well!

Am I likely to have a problem with the Python package I am using?

I am using Windows 10 and Python 3.9.2

Any help would be appreciated
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#2
It is working good to me,

mylist = [5, 12, 27, 3, 12, 5, 9, 5, 11]
print(mylist.count(5))
print(mylist.count(3))
print(mylist)

k=mylist.count(12)
print(k)
Output:
C:\Users\sandeep\Downloads>py test.py 3 1 [5, 12, 27, 3, 12, 5, 9, 5, 11] 2
Best Regards,
Sandeep.

GANGA SANDEEP KUMAR
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#3
mylist = [5, 12, 27, 3, 12, 5, 9, 5, 11]
print(mylist.count(3)) # Need print()
print(mylist)
Output:
1 [5, 12, 27, 3, 12, 5, 9, 5, 11]
mylist = [5, 12, 27, 3, 12, 5, 9, 5, 11]
count_number = 5
result = mylist.count(count_number)
print(f'There where {result} occurrences of <{count_number}> in:\n{mylist}')
Output:
There where 3 occurrences of <5> in: [5, 12, 27, 3, 12, 5, 9, 5, 11]
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#4
It is important that you understand that there are methods that work in-place (and return None) and others that return something like in this case - list.count() will return the result (if you want to use it, you need to bind it to a name, or print it, etc.)
If you can't explain it to a six year old, you don't understand it yourself, Albert Einstein
How to Ask Questions The Smart Way: link and another link
Create MCV example
Debug small programs

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#5
Thank you Sandeep_ganga, snippsat & Buran.
I get that - I was not using the print statement correctly not recognising I had called up print the original list and not the count result. However if I use mylist.reverse I have to revert to the my initial way of working as belowL
mylist = [5, 12, 27, 3, 12, 5, 9, 5, 11]
mylist.reverse()
print(mylist)
which gives the correct output of
Output:
[11, 5, 9, 5, 12, 3, 27, 12, 5]
Is this because I am using () in the call and not specifying anything between ()?

Thanks
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#6
(Mar-16-2021, 01:42 PM)Oldman45 Wrote: Is this because I am using () in the call and not specifying anything between ()?
no, it is because .reverse() method works in-place.
If you can't explain it to a six year old, you don't understand it yourself, Albert Einstein
How to Ask Questions The Smart Way: link and another link
Create MCV example
Debug small programs

Reply
#7
(Mar-16-2021, 01:42 PM)Oldman45 Wrote: Is this because I am using () in the call and not specifying anything between ()?
No it's because reverse() is modifying the original list in place.
So in case can not store it in a variable.
>>> mylist = [5, 12, 27, 3, 12, 5, 9, 5, 11]
>>> help(mylist.reverse)
Help on built-in function reverse:

reverse() method of builtins.list instance
    Reverse *IN PLACE*.

>>> rev = mylist.reverse()
>>> rev
>>> repr(rev)
'None'
>>> 
>>> mylist
[11, 5, 9, 5, 12, 3, 27, 12, 5]
count() is different as it return the result that can be stored in variable.
>>> mylist
[11, 5, 9, 5, 12, 3, 27, 12, 5]
>>> mylist = [5, 12, 27, 3, 12, 5, 9, 5, 11]
>>> help(mylist.count)
Help on built-in function count:

count(value, /) method of builtins.list instance
    Return number of occurrences of value.

>>> c = mylist.count(5)
>>> c
3 
Reply
#8
Buran, snippsat thanks for the education, I will now practice what I learnt. I really appreciate the support
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