iterables.py

numbers = [1, 2, 3, 4]

#############################
# general looping
#############################
for i in range(len(numbers)):
    print(numbers[i])

# should be
for num in numbers:
    print(num)

#############################
# reversed looping
#############################
list_len = len(numbers)

for i in range(list_len):
    print(numbers[list_len - i - 1])

# or...
for i in range(list_len - 1, -1, -1):
    print(numbers[i])

# should be
for num in reversed(numbers):
    print(num)

#############################
# certain range of list
#############################
for i in range(1, 3):
    print(numbers[i])

# should be
for num in numbers[1:3]:
    print(num)

#############################
# only elements with even indices
#############################
for i in range(len(numbers)):
    if i % 2 == 0:
        print(numbers[i])

# should be
for num in numbers[::2]:
    print(num)

#############################
# including indices
#############################
for i in range(len(numbers)):
    print(i, numbers[i])

# should be
for i, num in enumerate(numbers):
    print(i, num)

#############################
# two lists at once
#############################
numbers_2 = [5, 6, 7, 8]

for i in range(len(numbers)):
    print(numbers[i], numbers_2[i])

# should be
for num_1, num_2 in zip(numbers, numbers_2):
    print(num_1, num_2)

#############################
# dictionaries
#############################
data = {'name': 'bob', 'mail': 'bob@bobmail.com', 'address': 'bobstreet 12'}
for key in data:
    print(key, data[key])

# should be
for key, value in data.items():
    print(key, value)

# bonus
for value in data.values():
    print(value)

#############################
# list comprehensions
#############################
x_data = [1, 2, 3, 4]
y_data = []
for x in x_data:
    y_data.append(x**2)

# should be
x_data = [1, 2, 3, 4]
y_data = [x**2 for x in x_data]

# bonus
# initialize with 0
names = ['alice', 'bob', 'charlie']
name_count = {name: 0 for name in names}

# convert names to set
names_set = {name for name in names}

# add conditions to comprehension
l_names = [name for name in names if 'l' in name]
pour_bob = [name for name in names if len(name) < 4]

# although easy list comprehensions are really readable,
# they tend to get quite unreadable if they are longer and
# nested, so don't do this:
name = {name: [i for i in range(100) if i != 40] for name in names if
    len(name) > 3}