d = {"key1": 10, "key2": 23}
if "key1" in d: print("this will execute")
if "nonexistent key" in d: print("this will not")

# You can use 'in' on a dictionary to check if a key exists
d = {"key1": 10, "key2": 23}
"key1" in d
# Output:
# True

d = {"apples": 1, "banannas": 4}
# Preferably use .keys() when searching for a key
if "apples" in d.keys(): print(d["apples"])

if word in data: return data[word]
else: return "The word doesn't exist. Please double check it."

# define a dictionary
my_dict = {'a': 1, 'b': 2, 'c': 3}
# check if a key exists in the dictionary using the `in` operator
if 'a' in my_dict: print('Key exists') #print Key exists
else: print('Key does not exist')
# check if a key does not exist in the dictionary using the `in` operator
if 'd' not in my_dict: print('Key does not exist') #print Key does not exist
else: print('Key exists')
# check if a key exists in the dictionary using the `get()` method
value = my_dict.get('a')
if value is not None: print('Key exists') #print Key exists
else: print('Key does not exist')
# check if a key does not exist in the dictionary using the `get()` method
value = my_dict.get('d')
if value is None: print('Key does not exist') #print Key does not exist
else: print('Key exists')

# in tests for the existence of a key in a dict:
d = {"key1": 10, "key2": 23}
if "key1" in d: print("this will execute")
if "nonexistent key" in d: print("this will not")
# Use dict.get() to provide a default value when the key does not exist:
d = {}
for i in range(10): d[i] = d.get(i, 0) + 1
# To provide a default value for every key, either use dict.setdefault() on each assignment:
d = {}
for i in range(10): d[i] = d.setdefault(i, 0) + 1
# or use defaultdict from the collections module:
from collections import defaultdict
d = defaultdict(int)
for i in range(10): d[i] += 1