Have Geek Brain

Python: converting string to flags

If I have a string that is the result of a regexp mapping [MSP]*

, then what is the cleanest way to convert it to a dict containing the keys M, S and P, where the value of each key is true if the key appears in the string?

eg.

 'MSP' => {'M': True, 'S': True, 'P': True}
 'PMMM'   => {'M': True, 'S': False, 'P': True}
 ''    => {'M': False, 'S': False, 'P': False}
 'MOO'    won't occur... 
          if it was the input to matching the regexp, 'M' would be the output

The best I can think of is this:

 result = {'M': False, 'S': False, 'P': False}
 if (matchstring):
     for c in matchstring:
         result[c] = True

but this seems a little awkward, I was wondering if there is a better way.

+2


a source to share


2 answers


Why not use frozenset

(or set

if mutability is needed)?

s = frozenset('PMMM')
# now s == frozenset({'P', 'M'})

then you can use



'P' in s

to check if the flag exists P

.

+6


a source


In newer Python versions, you can use dict comprehension:

s = 'MMSMSS'
d = { c: c in s for c in 'MSP' }

On older versions, you can use this as KennyTM points out:



d = dict((c, c in s) for c in 'MSP')

This will give good performance for long lines, because if all three characters occur at the beginning of the line, the search may stop earlier. This does not require searching the entire string.

+3


a source






More articles:


All Articles