Using Python dict() to Create and Manipulate Dictionaries

The dict() function in Python creates a new dictionary and works similarly to the dict.update() method.

Syntax: dict(key/value) where key/value represents one or more key‑value pairs used to build the dictionary.

Examples:

# !/usr/bin/python3

# Create an empty dictionary

dict0 = dict()

print('dict0:', dict0)

# Create a dictionary with literal key/value pairs

dict1 = dict({ 'three': 3, 'four': 4 })

print('dict1:', dict1)

# Create a dictionary using keyword arguments

dict2 = dict(five=5, six=6)

print('dict2:', dict2)

# Create a dictionary from a list of tuples

dict3 = dict([('seven', 7), ('eight', 8)])

print('dict3:', dict3)

# Create a dictionary using zip()

dict5 = dict(zip(['eleven', 'twelve'], [11, 12]))

print('dict5:', dict5)

Output of the above examples:

dict0: {}

dict1: {'four': 4, 'three': 3}

dict2: {'five': 5, 'six': 6}

dict3: {'seven': 7, 'eight': 8}

dict5: {'twelve': 12, 'eleven': 11}

Common dictionary methods:

# clear() – empties the dictionary

stu = {'num1': 'Tom', 'num2': 'Lucy', 'num3': 'Sam'}

print(stu.clear()) # prints None

# copy() – returns a shallow copy

stu2 = stu.copy()

print('stu2:', stu2)

# fromkeys() – creates a new dict from a sequence of keys

names = ['tom', 'lucy', 'sam']

print(dict.fromkeys(names))

print(dict.fromkeys(names, 25)) # default value 25

# get() – retrieve value for a key

print(stu.get('num2')) # Lucy

# items() – returns a view of (key, value) pairs

print(stu.items())

# keys() – returns a view of keys

print(stu.keys())

# pop() – remove a key and return its value

name = stu.pop('num2')

print(name, stu)

# popitem() – remove and return an arbitrary (key, value) pair

pair = stu.popitem()

print(pair, stu)

# setdefault() – get value if key exists, otherwise insert key with default None

value = stu.setdefault('num5')

print(value, stu)

# update() – add or modify key‑value pairs

stu.update({'num4': 'Ben'})

print(stu)

These examples illustrate how to create dictionaries in various ways and manipulate them using built‑in methods.