Parse a map of int -> list from a string

Question

This should be a fairly straight forward python question, but I'm getting stuck getting the syntax right.

Let's say I have a string:

"1:a,b,c::2:e,f,g::3:h,i,j"

and I want to convert this to a map like so:

{'1': ['a', 'b', 'c'], '2': ['e', 'f', 'g'], '3': ['h', 'i', 'j']}

How would this be done?

I can figure out how to do it using nested for loops, but would be cool to just do it in a single line.

Thanks!

hint: have a look at string's split method which you can use to break your input string into chunks that you can further work on (perhaps with more calls to split) — stew
– stew, Commented Oct 12, 2010 at 20:38

Mark Byers · Accepted Answer · 2010-10-12 21:39:42Z

8

Here's one approach:

dict((k, v.split(',')) for k,v in (x.split(':') for x in s.split('::')))

edited Oct 12, 2010 at 21:39

answered Oct 12, 2010 at 20:38

Mark Byers

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4 Comments

user395760 Over a year ago

Horrible names, but otherwise perfect, +1

John Machin Over a year ago

@delnan: not quite perfect, use of list() is redundant

Mark Byers Over a year ago

@John Machin: Thanks for pointing that out. I wasn't sure if split returns a list in all versions of Python so was playing it safe. But I checked now and it seems that it always does. Fixed now. :)

user395760 Over a year ago

I wasn't sure either if split returned a list. They made nearly everything an iterator in Python 3 (which is a good thing) ;)

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