Comprehension in Python

dict_comp.py

my_dict = {i: i ** 2 for i in range(1, 11)}
-> {1: 1, 2: 4, 3: 9, 4: 16, 5: 25, 6: 36, 7: 49, 8: 64, 9: 81, 10: 100}
my_dict[7]
-> 49

gen.py

gen = (i ** i for i in range(1, 10))
print gen
-> <generator object <genexpr> at 0xfc7d20>
gen.next()
-> 1
gen.next()
-> 4
gen.next()
-> 27
gen.next()
-> 256

grid.py

rows = cols = range(3)
grid = [[(r, c) for c in cols] for r in rows]

-> [[(0, 0), (1, 0), (2, 0)],
    [(0, 1), (1, 1), (2, 1)],
    [(0, 2), (1, 2), (2, 2)]]

msg.py

msg = [['M', 'J', 'S', 'F'], ['A', 'O', 'O', 'O'], ['K', 'H', 'M', 'O'], ['E', 'N', 'E', 'D']]
' '.join(''.join(msg[j][i] for j in range(4)) for i in range(4))
-> 'MAKE JOHN SOME FOOD'

rows_cols.py

rows = cols = range(3)
grid = []
for r in rows:
    for c in cols:
        if r != c:
            cell = (r, c)
            grid.append(cell)
-> [(1, 0), (2, 0), (0, 1), (2, 1), (0, 2), (1, 2)]

rows_cols_comp.py

rows = cols = range(3)
grid = [(r, c) for c in cols for r in rows]
-> [(0, 0), (1, 0), (2, 0), (0, 1), (1, 1), (2, 1), (0, 2), (1, 2), (2, 2)]

grid = [(r, c) for c in cols for r in rows if r != c]
-> [(1, 0), (2, 0), (0, 1), (2, 1), (0, 2), (1, 2)]

set_comp.py

my_list = [i % 3 for i in range(10)]
-> [0, 1, 2, 0, 1, 2, 0, 1, 2, 0]

my_set = {i % 3 for i in range(10)}
-> set([0, 1, 2])

squares.py

squares = []
for n in range(10):
    squares.append(n ** 2)
-> [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

squares_comp.py

squares = [n ** 2 for n in range(10)]
-> [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

str_set_comp.py

char_list = [c for c in 'abracadabra']
-> ['a', 'b', 'r', 'a', 'c', 'a', 'd', 'a', 'b', 'r', 'a']

char_set = {c for c in 'abracadabra'}
-> set(['a', 'r', 'b', 'c', 'd'])

sum.py

sum(i ** 2 for i in range(10))
-> 285

>>> char_set = {i%3 for i in range(10)}
>>> char_set
set([0, 1, 2])

>>> char_list = [c for c in 'abracadabra']
>>> char_set = set(char_list)
>>> char_set
set(['a', 'r', 'b', 'c', 'd'])

Well spotted - thanks for pointing it out. Now fixed!