Dictionary in Python

Introduction

Dictionaries are used to store data values in key:value pairs. A dictionary is a collection which is ordered, changeable and do not allow duplicates.

Dictionaries are written with curly brackets, and have keys and values.

dict = {
  "Venezuela": "Caracas",
  "Argentina": "Buenos Aires",
  "Chile": "Santiego"
}
print(dict)

Building a Dictionary Incrementally

dict = {}
print(type(dict))
<class 'dict'>
dict["Venezuela"] = "Caracas"
dict["Philippines"] = "Manila"
dict["Argentina"] = "Buenos Aires"
dict["Chile"] = "Santiago"

Access Items

You can access the items of a dictionary by referring to its key name, inside square brackets:

print(dict["Philippines"])
print(dict.get("Philippines")
print(dict.keys())
print(dict.values())
print(dict.items())

Loop dictionary

for x in dict:
    print(x)

for x in dict:
    print(dict[x])

for x in dict.values():
    print(x)

for x in dict.keys():
    print(x)

for x,y in dict.item():
    print(x,y)    

Add Items

Adding an item to the dictionary is done by using a new index key and assigning a value to it:

dict = {}
dict["Chile"] = "Santiago"

Update Items

You can change the value of a specific item by referring to its key name. The update() method will update the dictionary with the items from the given argument. The argument must be a dictionary, or an iterable object with key:value pairs.

dict = {
  "Venezuela": "Caracas",
  "Argentina": "Buenos Aires",
  "Chile": "Santiego"
}
dict["Chile"] = "Manila"
dict.update({"Chile": "Manila"})

Remove Items

The pop() method removes the item with the specified key name:

thisdict = {
  "Philippines": "Manila",
  "Argentina": "Buenos Aires",
  "Chile": "Santiago"
}
thisdict.pop("Philippines")
print(thisdict)

The popitem() method removes the last inserted item (in versions before 3.7, a random item is removed instead):

thisdict = {
  "Philippines": "Manila",
  "Argentina": "Buenos Aires",
  "Chile": "Santiago"
}
thisdict.popitem()
print(thisdict)

The del keyword removes the item with the specified key name:

thisdict = {
  "Philippines": "Manila",
  "Argentina": "Buenos Aires",
  "Chile": "Santiago"
}
del thisdict["Chile"]
print(thisdict)