Question

going thru a tutorial on python lists,I tried to write a python function which counts the number of occurrences of words that start with a specific letter

def count_occurrences(p,letter):
    count = 0
    for elem in p:
        if elem[0]==letter:
            count = count+1
    return count


>>>count_occurrences(['damon','jim','dennis'],'d')
2
>>>count_occurrences(['damon','jim'],'d')
1
>>>count_occurrences([],'d')
0

but, if I input a list containing the wrong types,say [1,2,3] ,it will throw a TypeError:'int' object is unsubscriptable since the code elem[0] is called on an int.

So,how do I handle this? should I use a try : except block or is there another way?

Answer 1

add an isinstance() condition to your if comdition to check the type of elem:

def count_occurrences(p,letter):
    count = 0
    for elem in p:
        if isinstance(elem,str) and elem[0]==letter: #if the first condition is true then
                                                     # only it'll check the next condition
            count = count+1
    return count