将字符串列表中的字符映射到字典中，索引为键

Question

I'm asking to put a list of strings into a dictionary, such that the indices of the characters are the keys and the values are the combined characters.
I'm trying to get this as terse as I can.

My code:

a = ['apple','pear']
b = map(lambda x:dict(enumerate(x)),a)
print b

Output:

[{0: 'a', 1: 'p', 2: 'p', 3: 'l', 4: 'e'}, {0: 'p', 1: 'e', 2: 'a', 3: 'r'}]

Desired output:

{0:'ap',1:'pe',2:'pa',3:'lr',4:'e'}

Answer 1

you want zip

dict(enumerate(zip(*a)))

or maybe izip_longest

dict(enumerate(itertools.izip_longest(*a,fillvalue="")))

if you really need to you can join the letters easy enough

{k:"".join(v) for k,v in result.items()}

Answer 2

You can use itertools.zip_longest (in python 2 itertools.izip_longest ) within a dict comprehension :

>>> from itertools import zip_longest
>>> 
>>> {i:''.join(j) for i,j in enumerate(zip_longest(*a,fillvalue=''))}
{0: 'ap', 1: 'pe', 2: 'pa', 3: 'lr', 4: 'e'}

Answer 3

similar solution

{i: x+y for i, (x,y) in enumerate(zip_longest(*a,fillvalue=''))}

{0: 'ap', 1: 'pe', 2: 'pa', 3: 'lr', 4: 'e'}

Answer 4

Do you know if I can do this without the itertools import , yes map will work to catch the shorter string as you are using python2:

a = ['apple','pear']
b = {i: a + b if b else a  for i, (a, b) in enumerate(map(None,*a))}

print(b)
{0: 'ap', 1: 'pe', 2: 'pa', 3: 'lr', 4: 'e'}

To work for either a or b being different lengths we need a little more logic:

b = {i: a if not b else b if not a else a + b for i,(a, b) in enumerate(map(None, *a))}

map(None,*a) will behave somewhat like zip_longest , None will be used as a fillvalue for the shorter string. We just check if a or b is None and do the appropriate thing based on the result.