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 defaultdict example

>>> from collections import defaultdict
>>> ice_cream = defaultdict(lambda: 'Vanilla')
>>>
>>> ice_cream = defaultdict(lambda: 'Vanilla')
>>> ice_cream['Sarah'] = 'Chunky Monkey'
>>> ice_cream['Abdul'] = 'Butter Pecan'
>>> print ice_cream['Sarah']
Chunky Monkey
>>> print ice_cream['Joe']
Vanilla
>>>

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,{})

defaultdict python

>>> from collections import defaultdict
>>> food_list = 'spam spam spam spam spam spam eggs spam'.split()
>>> food_count = defaultdict(int) # default value of int is 0
>>> for food in food_list:
...     food_count[food] += 1 # increment element's value by 1
...
defaul

python defaultdict default value

d = defaultdict(lambda:1)

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

defaultdict in python

>>> s = [('yellow', 1), ('blue', 2), ('yellow', 3), ('blue', 4), ('red', 1)]
>>> d = defaultdict(list)
>>> for k, v in s:
...     d[k].append(v)
...
>>> d.items()
[('blue', [2, 4]), ('red', [1]), ('yellow', [1, 3])]

.defaultdict

>>> from collections import defaultdict
>>> food_list = 'spam spam spam spam spam spam eggs spam'.split()
>>> food_count = defaultdict(int) # default value of int is 0
>>> for food in food_list:
...     food_count[food] += 1 # increment element's value by 1
...
defaultdict(<type 'int'>, {'eggs': 1, 'spam': 7})
>>>

defaultdict in python

"""defaultdict allows us to initialize a dictionary that will assign a 
default value to non-existent keys. By supplying the argument int, 
we are able to ensure that any non-existent keys are automatically 
assigned a default value of 0."""

python defaultdict

# Python program to demonstrate
# defaultdict
  
  
from collections import defaultdict
  
  
# Function to return a default
# values for keys that is not
# present
def def_value():
    return "Not Present"
      
# Defining the dict
d = defaultdict(def_value)
d["a"] = 1
d["b"] = 2
  
print(d["a"]) # 1
print(d["b"]) # 2
print(d["c"]) # Not Present

python default dictionary

# 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