Filtering List Comprehensions
In this lesson, you’ll see that list comprehensions are often recommended by Python core developers as a more Pythonic solution than the filter() function you used in the previous lesson.
You can also skip the middle man and use a generator expression to get the same result but not create a list in the process. A generator expressions defines an ad hoc iterator that then produces values for you without first creating a list, and then creating a tuple from that list, and then destroying the list again, so it’s more memory efficient.
espdave4 on April 3, 2020
print(tuple(x for x in scientists if x.nobel is True)) TypeError: 'tuple' object is not callable George Yeboah on April 4, 2020
u missed the the tuple parentenses like the this print(tuple((x for x in scientists if x.nobel is True)))
So if tuple(filter(lambda x: x.nobel, scientist)) and tuple(x for x in scientist if x.nobel) return the same result, when should we use one over the other?
Dan Bader RP Team on April 20, 2020
Comprehensions are generally deemed as more Pythonic, so I’d go with this version:
tuple(x for x in scientist if x.nobel) (Technically, you’re writing a generator expression in this case but syntactically they’re the same as list comprehensions.)
quitobarajas on Aug. 5, 2020
seems a bit complicated but I’ll get the hang of it!
PrasadChaskar on Dec. 10, 2020
When we use list comprehensions the result is list, so can it mutable?
Bartosz Zaczyński RP Team on Dec. 11, 2020
@PrasadChaskar Yeah, absolutely. You just need to store the resulting value in a variable somewhere to be able to mutate it:
>>> squares = [i**2 for i in range(1, 10)] >>> squares[1] = "foobar" >>> squares [1, 'foobar', 9, 16, 25, 36, 49, 64, 81] Maram-dev on April 26, 2021
So the tuple(x for x in scientists if x.noble is True) didn’t generate the error you got from creating tuple(1,2,3) , because the expression (x for x. ) was taken for a single argument, right?
I’m a little bit new to Python, so excuse my sometimes stupid questions 🙂
Martin Breuss RP Team on April 26, 2021
Hi @Mar-dev, that’s a great question! 😀
And you’re right in your assumption. Using tuple() converts an iterable to a tuple and it takes only one argument as its input. The error message tells you that with tuple(1,2,3) you’re passing the three arguments 1 , 2 , and 3 , instead:
TypeError: tuple expected at most 1 argument, got 3 But what Dan did initially with the following line of code:
tuple(x for x in scientists if x.nobel is True) is that he created a generator object, which is a single, iterable object, and then he passed only that one argument to tuple() . So it worked ✨ 🙂
Maram-dev on April 27, 2021
Hey Martin, Thank you for the explanation! I will read more into generator objects, I still need to wrap my mind around them.
damipatira on Jan. 31, 2022
Cheers to List Comprehensions !! I have a feeling we will be good friends 😀