PYTHON

python default dictonary

from collections import defaultdict

d_int = defaultdict(int)
d_list = defaultdict(list)

def foo():
  return 'default value'
 
d_foo = defaultdict(foo)

>>> d_int
defaultdict(<type 'int'>, {})
>>> d_list
defaultdict(<type 'list'>, {})
>>> d_foo
defaultdict(<function foo at 0x7f34a0a69578>, {})

python dictionary default

# set default values for all keys
d = collections.defaultdict(lambda:1)
# set default value for a key if not exist - will not modify dictionary
value = d.get(key,default_value)
# if key is in the dictionary: return value
# else: insert the default value as well as return it
dict_trie.setdefault(char,{})

python dictonary set default

#!/usr/bin/python

dict = {'Name': 'Zara', 'Age': 7}
print "Value : %s" %  dict.setdefault('Age', None)
print "Value : %s" %  dict.setdefault('Sex', None)

>>Value : 7
>>Value : None

default dictionary value

>>> from collections import defaultdict
>>> d = {'foo': 123, 'bar': 456}
>>> d['baz']
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
KeyError: 'baz'
>>> d = defaultdict(lambda: -1, d)
>>> d['baz']
-1

set default dictionary in python

# sample code
monthConversions = {
    1: "January",
    2: "February",
    3: "March",
    4: "April",
    5: "May",
    6: "June",
    7: "July",
    8: "August",
    9: "September",
    10: "October",
    11: "November",
    12: "December"
}
num_month = int(input("Enter number of month: "))
# with default prompt if keys not found (keys,default value)
print(monthConversions.get(num_month,"Invalid input")) 

>>Enter number of month: 13
>>Invalid Input