Python equivalents to LINQ

Question

In C#, with LINQ, if I have en enumeration enumerable, I can do:

// a: Does the enumerable contain an item that satisfies the lambda? bool contains = enumerable.Any(lambda);  // b: How many items satisfy the lambda? int count = enumerable.Count(lambda);  // c: Return an enumerable that contains only distinct elements according to my custom comparer var distinct = enumerable.Distinct(comparer);  // d: Return the first element that satisfies the lambda, or throws an exception if none var element = enumerable.First(lambda);  // e: Returns an enumerable containing all the elements except those // that are also in 'other', equality being defined by my comparer var except = enumerable.Except(other, comparer); 

I hear that Python has a more concise syntax than C# (and is therefore more productive), so how do I achieve the same with an iterable in Python, with the same amount of code, or less?

Note: I don't want to materialize the iterable into a list if I don't have to (Any, Count, First).

Answer 1

The following Python lines should be equivalent to what you have (assuming func, or lambda in your code, returns a Boolean):

# Any contains = any(func(x) for x in enumerable)  # Count count = sum(func(x) for x in enumerable)  # Distinct: since we are using a custom comparer here, we need a loop to keep  # track of what has been seen already distinct = [] seen = set() for x in enumerable:     comp = comparer(x)     if not comp in seen:         seen.add(comp)         distinct.append(x)  # First element = next(iter(enumerable))  # Except except_ = [x for x in enumerable if not comparer(x) in other] 

References:

• List comprehensions
• Generator expressions
• any() built-in function
• sum() built-in function
• set type

Note that I renamed lambda to func since lambda is a keyword in Python, and I renamed except to except_ for the same reason.

Note that you could also use map() instead of the comprehensions/generators, but it is generally considered less readable.