Optimize double enumerate loops

Question

I want to optimize this code:

for MajorKey,v in enumerate(data):
    for MinorKey,e in enumerate(v['events']):
        if e['displayed'] == False:
            del data[MajorKey]['events'][MinorKey]

The structure:

data : [{ //details,
         "events" :[ { //more details,
                      "displayed" : True},
                      { //more details,
                      "displayed" : False}
                   ]
       },
       { //...
       }]

data is a list. Each object in data has an 'events' array. Of those objects I want to delete those that have display == false.

Answer 1

Don't enumerate, and don't delete (especially if you're iterating over the sequence you're deleting from). Slice-assign a list comprehension instead.

for v in data.itervalues():
  v['events'][:] = [e for e in v['events'] if e['displayed']]