Find common prefix ends with multiple suffix in python

Question

I have a list of string.

A = [
  'kite1.json',
  'kite1.mapping.json',
  'kite1.analyzer.json',
  'kite2.json',
  'kite3.mapping.json',
  'kite3.mapping.mapping.json',
  'kite3.mapping.analyzer.json',
 ]

I need to find common prefix which ends with all of .json, .mapping.json, .analyzer.json.

Here, kite1 & kite3.mapping are satisfied. But kite2 isn't, because it only ends with .json.

How can I find those prefix which ends with all of .json, .mapping.json, .analyzer.json.

Answer 1

If this were code-golf, I might win:

def ew(sx): 
   return set([s[:-len(sx)] for s in A if s.endswith(sx)])

ew('.analyzer.json') & ew('.mapping.json') & ew('.json')

The ew() function loops through A, finding all elements that end with the given suffix and stripping the suffix off, returning the results at a set.

Using it, I just calculate the intersection of the sets produced from each of the three suffixes. (& is the operator for intersection.)

For brevity's sake, I abbreviated "ends with" to ew and "suffix" to sx.

The expression s[:-len(sx)] means "the substring of s starting at 0 and going to len(sx) characters from the end", which has the effect of the snipping suffix off the end.

Answer 2

Well, all you need is to collect a set of prefixes for each suffix in ['.json', '.mapping.json', '.analyzer.json'] and then just take an intersection of these sets:

In [1]: A = [
   ...:   'kite1.json',
   ...:   'kite1.mapping.json',
   ...:   'kite1.analyzer.json',
   ...:   'kite2.json',
   ...:   'kite3.mapping.json',
   ...:   'kite3.mapping.mapping.json',
   ...:   'kite3.mapping.analyzer.json',
   ...:  ]

In [2]: suffixes = ['.json', '.mapping.json', '.analyzer.json']

In [3]: prefixes = {s: set() for s in suffixes}

In [4]: for word in A:
   ....:     for suffix in suffixes:
   ....:         if word.endswith(suffix):
   ....:             prefixes[suffix].add(word[:-len(suffix)])
   ....:             

In [5]: prefixes
Out[5]: 
{'.analyzer.json': {'kite1', 'kite3.mapping'},
 '.json': {'kite1',
  'kite1.analyzer',
  'kite1.mapping',
  'kite2',
  'kite3.mapping',
  'kite3.mapping.analyzer',
  'kite3.mapping.mapping'},
 '.mapping.json': {'kite1', 'kite3', 'kite3.mapping'}}

In [6]: prefixes['.json'] & prefixes['.mapping.json'] & prefixes['.analyzer.json']
Out[6]: {'kite1', 'kite3.mapping'}