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

i have dictionary following structure:

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

i want count in dictionary number of times 'key1' example appears first word in key tuple.

i started writing below mentioned code not think further:

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

any suggestion how should proceed ?

from collections import defaultdict  der = {('key1','key2'): 50, ('key3','key4'): 70, ('key1','key5'): 90}  b = defaultdict(int) item, ler in der:     b[item] += 1 print b         ## defaultdict(int, {'key1': 2, 'key3': 1}) print b['key1'] ## [2]  

python tuple operations , count