Check if a predicate evaluates true for all elements in an iterable in Python

Question

I am pretty sure there is a common idiom, but I couldn’t find it with Google Search…

Here is what I want to do (in Java):

// Applies the predicate to all elements of the iterable, and returns
// true if all evaluated to true, otherwise false
boolean allTrue = Iterables.all(someIterable, somePredicate);

How is this done “Pythonic” in Python?

Also would be great if I can get answer for this as well:

// Returns true if any of the elements return true for the predicate
boolean anyTrue = Iterables.any(someIterable, somePredicate);

Asked By: Enno Shioji

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Source

Answer 1

Do you mean something like:

allTrue = all(somePredicate(elem) for elem in someIterable)
anyTrue = any(somePredicate(elem) for elem in someIterable)

Answered By: eumiro

Answer 2

allTrue = all(map(predicate, iterable))
anyTrue = any(map(predicate, iterable))

Answered By: Don O'Donnell

Answer 3

You can use ‘all’ and ‘any’ builtin functions in Python:

all(map(somePredicate, somIterable))

Here somePredicate is a function and all will check if bool() of that element is True.

Answered By: Rafi

Answer 4

Here is an example that checks if a list contains all zeros:

x = [0, 0, 0]
all(map(lambda v: v==0, x))
# Evaluates to True

x = [0, 1, 0]
all(map(lambda v: v==0, x))
# Evaluates to False

Alternative you can also do:

all(v == 0 for v in x)

Answered By: Rafael

Check if a predicate evaluates true for all elements in an iterable in Python

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