CODEWITHSUNDEEP
pythonlistfor-loop
David López
David López

Reputation: 531

If all elements match requirement not using "if all"

I am learning python with a book: The exercise is to make a program that print True if all numbers in a list all odds.

I get it whit this approach

if all(x % 2 == 1 for x in list):

But the 'if all' approach is not yet explained. They only use while, if,for and booleans in the examples. Furthermore, seems to be a reflexive exercise about it is possible to do it, maybe not. It is possible to do it using the basic tools of above?

Upvotes: 3

Views: 71

Answers (2)

Roland Illig
Roland Illig

Reputation: 41686

Yes, it is possible.

The Python code you wrote is very idiomatic, keep up that good work.

To see how to do it differently, you can look at programming languages that are less advanced, such as C. That is a very basic programming language which lacks the features for this if all statement. Searching for "c all elements array true" should give you the code you are looking for. For such a simple piece of code, it's easy to translate the code back into Python.

Upvotes: 4

Devesh Kumar Singh
Devesh Kumar Singh

Reputation: 20500

If you look at the docs: https://docs.python.org/3/library/functions.html#all

all(iterable) .
Return True if all elements of the iterable are true (or if the iterable is empty). Equivalent to:

def all(iterable):
    for element in iterable:
        if not element:
            return False
    return True

So if all(x % 2 == 1 for x in li): roughly translates to

def are_all_odds(num_list):

    #Flag to keep track if we encounter an even number
    flag = True
    for num in num_list:
        #Once we encounter a even number, we break the for loop
        if num % 2 != 1:
            flag = False
            break

    #Return the flag
    return flag

We can test this function by doing

print(are_all_odds([1, 2, 3, 4]))
#False
print(are_all_odds([1, 3, 5]))
#True

Also just a suggestion, list is a python builtin keyword, so don't use it in variables :)

Upvotes: 4

Related Questions