list expression python code example

Example 1: python list comprehension

nums = [4, -7, 9, 1, -1, 8, -6]
half_of_nums = [x/2 for x in nums] #[2, -3.5, 4.5, 0.5, -0.5, 4, -3]

#optionally you can add an if statement like this
half_of_positive_nums = [x/2 for x in nums if x>=0] #[2, 4.5, 0.5, 4]

Example 2: python list comprehension

#example: removing common elements found in `a` from `b`.
a = [1,2,3,4,5]
b = [5,6,7,8,9]
# desired output: [1,2,3,4]

# gets each item found in `a` AND not in `b`
print([i for i in a if i not in b])

Example 3: list comprehension

# List comprehension 

        
list_comp = [i+3 for i in range(20)]

# above code is similar to 

for i in range(20):
	print(i + 3)

Example 4: x for x in python

# This could be said as:
x for x in thing: 
# Or
for x in thing:
    return x # Or whatever that puts x in some variable

# Same thing, just really dodgy syntax.