#create a new list from an existing one that only keeps long words (>3 letters)
words = 'My cat is black and I like her.'.split()
long_words = [word for word in words if len(word) > 3]


#how many long words are there?
sum([1 for word in words if len(word) > 3])
len([5 for word in words if len(word) > 3]) #len(long_words)



[(thing to keep) for variable in list {if condition is True}]

#without if clause
new_list = []
for variable in list:
    new_list.append(thing to keep)

#with if clause
new_list = []
for variable in list:
    if condition is True:
        new_list.append(thing to keep)


[val*val for val in range(1, 6)]
new_list = []
for val in range(1, 6):
    new_list.append(val*val)