Data Science
What is Python dictionary in Python
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" |
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