python - python dict comprehension with two ranges

Question

I'm trying to produce some code that produces for example:

{1:7,2:8,3:9,4:10}

and

{i:j for i in range(1,5) for j in range(7,11)}

produces

{1: 10, 2: 10, 3: 10, 4: 10}

how can I fix it?

thanks

Answer 1

Using zip:

>>> dict(zip(range(1,5), range(7,11)))
{1: 7, 2: 8, 3: 9, 4: 10}

Using dict comprehension:

>>> {k:v for k, v in zip(range(1,5), range(7,11))}
{1: 7, 2: 8, 3: 9, 4: 10}

>>> {x:x+6 for x in range(1,5)}
{1: 7, 2: 8, 3: 9, 4: 10}

Why your code does not work:

Your code is similar to following code:

ret = {}
for i in range(1,5):
    for j in range(7,11):
        ret[i] = j
    # ret[i] = 10 is executed at last for every `i`.

Answer 2

{i: j for i, j in zip(range(1, 5), range(7, 11))}

Answer 3

Using zip(or itertools.izip) and itertools.count:

>>> from itertools import count, izip

Dict-comprehension:

>>> {k:v for k,v in izip(xrange(1,5), count(7))}
{1: 7, 2: 8, 3: 9, 4: 10}

dict():

>>> dict(izip(xrange(1,5), count(7)))
{1: 7, 2: 8, 3: 9, 4: 10}

Answer 4

I would use enumerate:

>>> dict(enumerate(range(7, 11), 1))
{1: 7, 2: 8, 3: 9, 4: 10}