Python: Comparing values in a defaultdict(set)

Question

I have a defalutdict(set) that stores a set of users, and for each user a set of events, and a timestamp for each event. What I need to do is check the timestamp of the item in the defaultdict and if it falls outside a specific time then remove it from the dict.

The defaultdict[player] looks like this:

set([('event1', <function timestampToEpoch at 0x102f8b758>), 
     ('event3', <function timestampToEpoch at 0x102f8b758>),
     ('event2', <function timestampToEpoch at 0x102f8b758>)]))

The code I'm trying to use looks like:

def removeUnique(player, f_Type, num_seconds, ts):
    curTime = timestampToEpoch(ts)
    for e in uniqueFishes[player] if e <= curTime - num_seconds
            uniqueFishes[player].remove(e)
    print uniqueFishes[player]

Answer 1

As you mentioned the two errors:

1) line 73 for e in uniqueFishes[player] if e >= (curTime - num_seconds) ^ SyntaxError: invalid syntax

2) Set changed size during iteration

.

change

for e in uniqueFishes[player] if e >= curTime - num_seconds
        uniqueFishes[player].remove(e)

to :

to_remove_set = set()
for e in uniqueFishes[player]:
    if e[1] >= (curTime - num_seconds):
        to_remove_set.add(e)

# modify your set after iteration.
uniqueFisihes[player] -= to_remove_set

Answer 2

Put your if function in the loop.

Your e variable is not a timestamp, but a tuple of a string and a timestamp. You get the timestamp with selecting the 2nd item of the tuple: e[1] .

You modify an iterable ( uniqueFishes ) while iterating over it. It is always a bad idea. Easiest (but not most efficient) solution for this is to iterate over a COPY of the original set while modifying the set itself.

def removeUnique(player,f_Type,num_seconds,ts):
   curTime = timestampToEpoch(ts)
   for e in uniqueFishes[player].copy():
      if e[1] >= curTime - num_seconds: 
         uniqueFishes[player].remove(e)
   print uniqueFishes[player]

Answer 3

Use a list comprehension:

[uniqueFishes[player].remove(e) for e in uniqueFishes[player] 
 if e >= (curTime - num_seconds)]