Answered Request for Help with List Methods in Python

[CodingNovice]

Please find attached a screenshot of an error message pertaining to my code from an exercise in list methods in Python, specifically count() and index(). If anyone has any constructive criticisms or suggestions, I will be most grateful. Many thanks in advance for all your help.

 

[skifli]

Please find attached a screenshot of an error message pertaining to my code from an exercise in list methods in Python, specifically count() and index(). If anyone has any constructive criticisms or suggestions, I will be most grateful. Many thanks in advance for all your help.

areas = [11.25, 18.0, 20.0, 10.75, 9.50]

# Print out the index of the element 20.0
print(str(areas.index(20.0)))

# Print out how often 9.50 appears in areas
print(str(areas.count(9.50)))

You use `.index(num)` on a list to get the index of that element in the list. Also for `.count()`, the variables in `areas` are floats, so make sure you do `.count(9.50)`, not `.count("9.50")`. Also there is no real need to convert the index and count to strings, but I left it there in case the challenge required the output to be a string.

 

[simong1993]

Hey, So part of what didlly is saying is correct BUT this is not a INT this is a Float. Int would be 1 where as a float is 1.00. Best to get this sorted before you get too far along 😀 but lets first dig into whats happening here and why you are having issues 😀


So the first bit you did :-

print(str(areas.index([-3])))

What you are doing here is trying to get option 3 from a list but its not a list and not coded correctly if you did want to get option 3 you would do this :-

print(areas[-3])

But this is not what you need, so lets move onto what it should be:-

print(areas.index(20.0))

nice and easy 🙂 now the next bit:-

print(str(areas.count('9.50')))

although your code is correct it wont work. as soon as you put '9.50' you turned that into a string, but in your list it is a float so it will return nothing. But if you do :-

print(areas.count(9.50)

this will work. also just for the future if you do

print(type(areas))

this will tell you areas is a list, if you replace areas with 9.50 this will tell you its a float and if you do 9 this is a int and '9.50' is a string 🙂

 

[CodingNovice]

areas = [11.25, 18.0, 20.0, 10.75, 9.50]

# Print out the index of the element 20.0
print(str(areas.index(20.0)))

# Print out how often 9.50 appears in areas
print(str(areas.count(9.50)))

You use `.index(num)` on a list to get the index of that element in the list. Also for `.count()`, the variables in `areas` are integers, so make sure you do `.count(9.50)`, not `.count("9.50")`. Also there is no real need to convert the index and count to strings, but I left it there in case the challenge required the output to be a string.

Many thanks! Problem solved. (The second part of the exercise was correct on the first attempt.) 🙂

 

[CodingNovice]

Hey, So part of what didlly is saying is correct BUT this is not a INT this is a Float. Int would be 1 where as a float is 1.00. Best to get this sorted before you get too far along 😀 but lets first dig into whats happening here and why you are having issues 😀


So the first bit you did :-

print(str(areas.index([-3])))

What you are doing here is trying to get option 3 from a list but its not a list and not coded correctly if you did want to get option 3 you would do this :-

print(areas[-3])

But this is not what you need, so lets move onto what it should be:-

print(areas.index(20.0))

nice and easy 🙂 now the next bit:-

print(str(areas.count('9.50')))

although your code is correct it wont work. as soon as you put '9.50' you turned that into a string, but in your list it is a float so it will return nothing. But if you do :-

print(areas.count(9.50)

this will work. also just for the future if you do

print(type(areas))

this will tell you areas is a list, if you replace areas with 9.50 this will tell you its a float and if you do 9 this is a int and '9.50' is a string 🙂

Many thanks! In particular, thanks for the step-by-step explanation. I applied this information successfully not only to the first part of the exercise (this one) but to the second part of the exercise on the first attempt. 🙂