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Comprehensions & generators

List/dict/set comprehensions, generator expressions, and lazy iteration.

3 matches

How to Filter Data with Predicates in Python

This helper filters a list with a predicate using a list comprehension, plus a lazy generator version that yields matches one by one.

filtering comprehensions generators

Python

def filter_data(data, predicate):
    """Return a list containing only items that pass the predicate."""
    return [item for item in data if predicate(item)]


def filter_data_lazy(data, predicate):
    """Generator version: yields items that pass the predicate one by one."""
    for item in data:
        if predicat…

16 0 Open

Comprehensions & generators medium

How to filter a generator with a predicate function in Python

This code defines a generator function that yields only items from an iterable that satisfy a given predicate, then tests it with even and positive number filters.

generators filtering lazy evaluation

Python

def filter_gen(predicate, iterable):
    for item in iterable:
        if predicate(item):
            yield item

def is_even(num):
    return num % 2 == 0

def is_positive(num):
    return num > 0

if __name__ == "__main__":
    numbers = range(-5, 10)
    
    even_numbers = list(filter_gen(is_even, numbers))
    p…

10 0 Open

Comprehensions & generators easy

How to skip items until a condition is met in Python

Use itertools.dropwhile to skip leading elements while a predicate returns true, then yield the rest of the sequence unchanged.

itertools generators dropwhile

Python

def is_negative(x):
    return x < 0

numbers = [-3, -1, 0, 5, 2, -8, 7]
result = list(itertools.dropwhile(is_negative, numbers))
print(f"Original: {numbers}")
print(f"After dropwhile: {result}")

13 0 Open

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