Question: I want to convert a string such as 'a=b,a=c,a=d,b=e' into a dict of lists {'a': ['b', 'c', 'd'], 'b': ['e']} in Python 2.6.

My current solution is this:

```
def merge(d1, d2):
    for k, v in d2.items():
        if k in d1:
            if type(d1[k]) != type(list()):
                d1[k] = list(d1[k])
            d1[k].append(v)
        else:
            d1[k] = list(v)
    return d1

record = 'a=b,a=c,a=d,b=e'

print reduce(merge, map(dict,[[x.split('=')] for x in record.split(',')]))

```

which I'm sure is unnecessarily complicated.

Any better solutions?

Answer: 
```
>>> result={}
>>> mystr='a=b,a=c,a=d,b=e'
>>> for k, v in [s.split('=') for s in mystr.split(',')]:
...     result[k] = result.get(k, []) + [v]
... 
>>> result
{'a': ['b', 'c', 'd'], 'b': ['e']}

```
How about...

```
STR = "a=c,b=d,a=x,a=b"
d = {} # An empty dictionary to start with.

# We split the string at the commas first, and each substr at the '=' sign
pairs = (subs.split('=') for subs in STR.split(','))

# Now we add each pair to a dictionary of lists.
for key, value in pairs:
    d[key] = d.get(key, []) + [value]

```