Check how many times a key of a tuple repeats itself in a dict?

Question

I have a dictionary with the following structure:

{('key1','key2'): 50, ('key3','key4'): 70, ('key1','key5'): 90.....}

I want to count in my dictionary the number of times 'key1' for example appears as the first word in the key tuple.

I started writing the below mentioned code but could not think further:

  count = 0 
  leng = 0 
  i = 0 
  for key1,key2 in range(1,len(bigrams)):
      count = count +1 
      leng = leng + (bigrams.get((key1,key2),0))  
  print(count) 
  print(leng)

Any suggestion as to how should I proceed ?

Answer 1

from collections import defaultdict

der = {('key1','key2'): 50, ('key3','key4'): 70, ('key1','key5'): 90}

b = defaultdict(int)
for item, ler in der:
    b[item] += 1
print b         ## defaultdict(int, {'key1': 2, 'key3': 1})
print b['key1'] ## [2] 

Python tuple operations and count

Answer 2

I'd use sum() with a generator expression to iterate over the keys, testing each one in turn:

bigrams = {('key1','key2'): 50, ('key3','key4'): 70, ('key1','key5'): 90}

def number_of_times_key_appears_as_first_word(key, dictionary):
    return sum(k[0] == key for k in dictionary)

assert number_of_times_key_appears_as_first_word('key1', bigrams) == 2
assert number_of_times_key_appears_as_first_word('key3', bigrams) == 1
assert number_of_times_key_appears_as_first_word('key2', bigrams) == 0

Answer 3

You can use collections.Counter to count each part of the keys as the following:

from collections import Counter
dic = {('key1','key2'): 50, ('key3','key4'): 70, ('key1','key5'): 90}
keys_0 = Counter(key[0] for key in dic.keys())
keys_1 = Counter(key[1] for key in dic.keys())

# keys_0 = Counter({'key1': 2, 'key3': 1})
# keys_1 = Counter({'key2': 1, 'key4': 1, 'key5': 1})

You can type cast counter object to a dict if you want by using dict(Counter(...))

Answer 4

Below one gives the required count:

dict1 = {('key1','key2'): 50, ('key3','key4'): 70, ('key1','key5'): 90, ('key3','key1'): 90}
count = 0
for keys in dict1.keys():
    if 'key1' in keys:
        if (keys[0] == 'key1'):
            count = count + 1
print count