d = dict()

for i in range(100):
    key = i % 10
    if key in d:
        d[key] += 1
    else:
        d[key] = 1

d = dict()

for i in range(100):
    key = i % 10
    d[key] = d.get(key, 0) + 1

from collections import defaultdict

d = defaultdict(int)

for i in range(100):
    d[i % 10] += 1

if 'key1' in dict:
  print "blah"
else:
  print "boo"

d = {'a': 1, 'b': 2}
'a' in d # 

if 'key1' in dict:
    ...

>>> d = {'foo':'bar'}
>>> q = d.setdefault('foo','baz') #Do not override the existing key
>>> print q #The value takes what was originally in the dictionary
bar
>>> print d
{'foo': 'bar'}
>>> r = d.setdefault('baz',18) #baz was never in the dictionary
>>> print r #Now r has the value supplied above
18
>>> print d #The dictionary's been updated
{'foo': 'bar', 'baz': 18}

values = {...}
myValue = values.get('Key', None)

try:
   blah = dict["mykey"]
   # key exists in dict
except KeyError:
   # key doesn't exist in dict

message = "blah" if 'key1' in dict else "booh"
print(message)

try:
    my_dict_of_items[key_i_want_to_check]
except KeyError:
    # Do the operation you wanted to do for "key not present in dict".
else:
    # Do the operation you wanted to do with "key present in dict."

if dict.has_key('xyz')==1:
    #update the value for the key
else:
    pass

d = defaultdict(int)

d={'clear':0, 'copy':1, 'fromkeys':2, 'get':3, 'items':4, 'keys':5, 'pop':6, 'popitem':7, 'setdefault':8, 'update':9, 'values':10}

Python Dictionary clear()       Removes all Items
Python Dictionary copy()        Returns Shallow Copy of a Dictionary
Python Dictionary fromkeys()    Creates dictionary from given sequence
Python Dictionary get()         Returns Value of The Key
Python Dictionary items()       Returns view of dictionary (key, value) pair
Python Dictionary keys()        Returns View Object of All Keys
Python Dictionary pop()         Removes and returns element having given key
Python Dictionary popitem()     Returns & Removes Element From Dictionary
Python Dictionary setdefault()  Inserts Key With a Value if Key is not Present
Python Dictionary update()      Updates the Dictionary 
Python Dictionary values()      Returns view of all values in dictionary

d.get("key")

d= {'clear':0, 'copy':1, 'fromkeys':2, 'get':3, 'items':4, 'keys':5, 'pop':6, 'popitem':7, 'setdefault':8, 'update':9, 'values':10}

print(d.get('key')) #None
print(d.get('clear')) #0
print(d.get('copy')) #1

d= {'key':None}
print(d.get('key')) #None
print(d.get('key2')) #None

print('key' in d) #True
print('key2' in d) #False

import dis
dis.dis("'key' in d")
#   1           0 LOAD_CONST               0 ('key')
#               2 LOAD_NAME                0 (d)
#               4 COMPARE_OP               6 (in)
#               6 RETURN_VALUE

dis.dis("d.get('key2')")
#   1           0 LOAD_NAME                0 (d)
#               2 LOAD_METHOD              1 (get)
#               4 LOAD_CONST               0 ('key2')
#               6 CALL_METHOD              1
#               8 RETURN_VALUE

 >>> temp = {}

 >>> help(temp.__contains__)

Help on built-in function __contains__:

__contains__(key, /) method of builtins.dict instance
    True if D has a key k, else False.

d = {'a': 1, 'b':2}
keys = 'abcd'

for k in keys:
    x = (k in d and 'blah') or 'boo'
    print(x) 

>>> blah
>>> blah
>>> boo
>>> boo

>>> 'Some string' or 1/0 
'Some string'
>>>

>>> 1/0 or 'Some string'
Traceback (most recent call last):
  File "", line 1, in 
ZeroDivisionError: division by zero
>>> 

(k in d and 'blah')

if k in d:
    'blah'
else:
    False

>>> False or 'boo'
'boo'
>>> 'blah' or 'boo'
'blah'
>>> 

dic = {'first' : 12, 'second' : 123}
for each in dic:
    if each == 'second': 
        print('the key exists and the corresponding value can be updated in the dictionary')