Dealing With Lists

Lists are a big part of Python, so various list techniques make your code more Pythonic.

You can initiate or create a list in a simple way using the * operator.

arr = [1] * 3  # arr = [1, 1, 1]

Using for loop you can filter or map and create list in a more pythonic way,

numbers = [1, 2, -3, -2, 5]

# filter numbers list to hold only positive numbers
# filtered_list = [1, 2, 5]
filtered_list = [num for num in numbers if num > 0]

# map numbers to array of their power of 2
# mapped_list = [1, 4, 9, 4, 25]
mapped_list = [num * num for num in numbers]

You can map and filter in same time!

positive_and_power = [num * num for num in numbers if num > 0]

When using () instead of [] python will create generator instead of list

filtered_gen = (num for num in numbers if num > 0)
print(next(filtered_gen))  # 1
print(next(filtered_gen))  # 2
print(next(filtered_gen))  # 5