list.count does not appear to function

list.count does not appear to function - Printable Version

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list.count does not appear to function - Oldman45 - Mar-16-2021

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

RE: list.count does not appear to function - sandeep_ganga - Mar-16-2021

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

RE: list.count does not appear to function - snippsat - Mar-16-2021

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]

RE: list.count does not appear to function - buran - Mar-16-2021

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.)

RE: list.count does not appear to function - Oldman45 - Mar-16-2021

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

RE: list.count does not appear to function - buran - Mar-16-2021

(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.

RE: list.count does not appear to function - snippsat - Mar-16-2021

(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

RE: list.count does not appear to function - Oldman45 - Mar-16-2021

Buran, snippsat thanks for the education, I will now practice what I learnt. I really appreciate the support