How can I check if an element is in a list?

Question

Python

I need to get a list of people matching person : start date but I need people only for a certain parameter. Parameter:

uidpay = list(db.events.distinct("uid", {"is_buyer": 1}))

and his example:

[u'6210A609-03CD-4646-9B69-D6F0C455D5E7', u'14738D3A-E80E-4A51-97A9-787E646AEF18']

. This is how I get the start time:

lel = list(db.events.aggregate(
[
  {"$match": {"eventName" : "Level 1"}},
  {"$group": {"_id": "$uid", "dateofstart": {"$addToSet": "$updated_at"}}}
]))

Here is an example output (already done in a convenient way):

meh = [{"u'F829CB26-CF2B-4896-92D6-17B1519948C7'": u'F829CB26-CF2B-4896-92D6-17B1519948C7'}, {"u'6071a6fb-4d93-4589-84a7-8a8c8ce37094'": u'6071a6fb-4d93-4589-84a7-8a8c8ce37094'}]

and I'm trying to build a check like this:

for players in meh:
  kost = str(players.keys())
  print(kost)
  kost = kost[2:41]
  print(kost)
  if kost == uidpay:
    dateoflvl1pay.append(players)
print(dateoflvl1pay)

I understand that the code is bad, but still the question is how to correctly check for the presence of elements in the list?