Python Dictionary

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Python Dictionary:

A dictionary is a collection or an associative array which is used to store various types of data.

Features of Python Dictionaries:

  • They are unordered and changeable.
  • They are written within curly brackets.
  • They can store multiple types of data.
  • They are mutable. Thus, the current values in the dictionary can be modified.
  • Keys are immutable. Thus, it can not be modified.
  • Python Dictionaries supports various operations.
  • The complete pair of key and value is called as a dictionary item.
  • The key passed in each dictionary item must be unique.
  • The key and the value is separated by a colon(:).
  • Items are separated from each other by a comma(,).
  • Value in a dictionary can be accessed by its key.

Python Dictionaries Methods:

METHODS USES
clear() To remove all the elements from the dictionary.
cmp() To compare two dictionaries.
copy() To get a copy of the dictionary.
fromkeys() To get a dictionary with the specified keys and values.
get() To get the value of the specified key.
items() To get a list containing the a tuple for each key value pair.
 keys() To get a list containing the dictionary’s keys.
len() To get the number of items in a dictionary.
pop() To get the element with the specified key.
 popitem() To remove the last key-value pair.
setdefault() To get the value of the specified key. If the key does not exist: insert the key, with the specified value.
str() To get the string representation of a dictionary.
update() To update the dictionary with the specified key-value pairs.
values() To get a list of all the values in the dictionary.

Example:

a =  { "1": "python",
"2": "java",
  "3": "php",
   "4": "HTML",
    "5": "javascript",
     "6": "CSS",
      "7": "Bootstrap"}
print "\n"
print "Dictionary is:"
print a
print "\n"
 
print "Get the value of the key 1."
print(a["1"])
print "\n"
 
print "Get the total length."
print(len(a))
print "\n"
 
print "Delete the item."
del a["5"]
print a
print "\n"
 
print "Replace a value."
a["3"] = "jQuery"
print a
print "\n"
 
print "Add a value."
a["9"] = "C"
print a
print "\n"

Output: