How to map list of strings containing key value to dict in Python?

Question

My list contains the following elements:

>>> s = "foo a=b c=d e=f"
>>> s.split()
['set', 'a=b', 'c=d', 'e=f']
>>> splitted = s.split()
>>> splitted[1:]
['a=b', 'c=d', 'e=f']

Now I want to use map to get the following result:

[{'a': 'b'}, {'c': 'd'}, {'e': 'f'}]

I tried the following, but this gives me an IndexError:

>>> map(lambda x : dict((a[0], a[1]) for a in x.split('=')) , splitted[1:])

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 1, in <lambda>
  File "<stdin>", line 1, in <genexpr>
IndexError: string index out of range

Please provide a minimal example. Also, there are several indexing operations, which of them raises the exception? — Ulrich Eckhardt, Jan 08 '18 at 09:32

score 6 · Accepted Answer · answered Jan 08 '18 at 09:35

You don't want to iterate over what you've split, just wrap that in an iterable, like a tuple:

>>> splitted
['a=b', 'c=d', 'e=f']
>>> [dict((x.split('='),)) for x in splitted]
[{'a': 'b'}, {'c': 'd'}, {'e': 'f'}]

I.E.

(x.split('='),)

Is a tuple with one element, the result of .spliting on the '=' sign.

Or using map and lambda:

>>> list(map(lambda x: dict((x.split('='),)), splitted))
[{'a': 'b'}, {'c': 'd'}, {'e': 'f'}]

I will say, this seems like a rather un-useful data-structure.

To be clear, your construction fails because you are iterating too deeply. The generator expression:

(a[0], a[1]) for a in x.split('=')

Is iterating over x.split('='), which in this case is always a list with two elements, length-1 strings, e.g. ['a','b'].

Your second method raise error `TypeError: 'dict' object is not callable` on python 3.x, can you confirm? — Sohaib Farooqi, Jan 08 '18 at 09:40
@GarbageCollector no, it doesn't, you probably have done `dict = ` somewhere in your interpreter session/script — juanpa.arrivillaga, Jan 08 '18 at 09:43

score 1 · Answer 2 · answered Jan 08 '18 at 09:35

1

You may create a simple list comprehension to achieve this. Here you need to split each string based on = and type-cast it to dict. For example:

>>> my_list = ['a=b', 'c=d', 'e=f']

>>> [dict([my_str.split('=')])  for my_str in my_list]
[{'a': 'b'}, {'c': 'd'}, {'e': 'f'}]

Here's the working working version of your solution using lambda:

#     actually you don't need to iterate here v
>>> list(map(lambda x : dict([[a for a in x.split('=')]]) , my_list))
[{'a': 'b'}, {'c': 'd'}, {'e': 'f'}]

This could be simplified as:

>>> list(map(lambda x : dict([x.split('=')]) , my_list))
[{'a': 'b'}, {'c': 'd'}, {'e': 'f'}]

answered Jan 08 '18 at 09:35

Moinuddin Quadri

46,825
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Your second and third method raise error `TypeError: 'dict' object is not callable` on python 3.x, can you confirm? – Sohaib Farooqi Jan 08 '18 at 09:42
@GarbageCollector It works for me. I am using Python 3.4.1 – Moinuddin Quadri Jan 08 '18 at 09:42
Yes sorry about this, I think there was some naming conflict in my python shell. Works perfectly. – Sohaib Farooqi Jan 08 '18 at 09:45
1

@GarbageCollector take a look at this https://stackoverflow.com/questions/46263897/how-to-reassign-dict-functionality-back-to-the-dict – Bharath M Shetty Jan 08 '18 at 09:56

score 0 · Answer 3 · answered Jan 08 '18 at 10:06

0

You can use zip function:

result= list(map(lambda x: dict(zip(*x.split('='))) ,splitted[1:]))

OR

needed = list(dict(zip(*x.split('='))) for x in splitted[1:])

answered Jan 08 '18 at 10:06

DARK_C0D3R

2,075
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How to map list of strings containing key value to dict in Python?

3 Answers3