What is correct syntax to create Python dictionary?

A Dictionary is a collection of key-value pairs, where each key is separated from its value by a colon ":" and items are separated by commas. Dictionary keys must be unique and since Python 3.7, dictionaries maintain insertion order.

The correct syntax to create a Python dictionary is to store values in key-value pairs within curly braces { }. Keys appear on the left of the colon, values on the right, and items are separated by commas.

Basic Syntax

The fundamental syntax for creating a dictionary in Python ?

my_dict = {
    "key1": "value1",
    "key2": "value2",
    "key3": "value3"
}

Creating Dictionary with Multiple Key-Value Pairs

Dictionary with 4 Key-Value Pairs

Here's an example with keys Product, Model, Units, and Available ?

# Creating a Dictionary with 4 key-value pairs
product_info = {
    "Product": "Mobile",
    "Model": "XUT",
    "Units": 120,
    "Available": "Yes"
}

print("Dictionary =", product_info)

Dictionary = {'Product': 'Mobile', 'Model': 'XUT', 'Units': 120, 'Available': 'Yes'}

Dictionary with 5 Key-Value Pairs

Adding one more key-value pair to the previous example ?

# Creating a Dictionary with 5 key-value pairs
product_info = {
    "Product": "Mobile",
    "Model": "XUT", 
    "Units": 120,
    "Available": "Yes",
    "Grade": "A"
}

print("Dictionary =", product_info)

Dictionary = {'Product': 'Mobile', 'Model': 'XUT', 'Units': 120, 'Available': 'Yes', 'Grade': 'A'}

Different Key Types

Dictionary with String Keys

String keys are the most common type, where each key is a text label ?

person = {
    "name": "Niharika",
    "age": 30,
    "city": "New York",
    "company": "TutorialsPoint"
}

print("Type:", type(person))
print("Dictionary =", person)

Type: <class 'dict'>
Dictionary = {'name': 'Niharika', 'age': 30, 'city': 'New York', 'company': 'TutorialsPoint'}

Dictionary with Integer Keys

Integer keys can be useful for numerical mappings ?

subjects = {
    101: "Math",
    102: "Science", 
    103: "History"
}

print("Type:", type(subjects))
print("Dictionary =", subjects)

Type: <class 'dict'>
Dictionary = {101: 'Math', 102: 'Science', 103: 'History'}

Mixed Data Type Dictionary

Python dictionaries can contain different data types for both keys and values ?

mixed_dict = {
    "name": "Niharika",
    1: [10, 20, 30],
    "is_active": True,
    3.14: "pi"
}

print("Type:", type(mixed_dict))
print("Dictionary =", mixed_dict)

Type: <class 'dict'>
Dictionary = {'name': 'Niharika', 1: [10, 20, 30], 'is_active': True, 3.14: 'pi'}

Creating an Empty Dictionary

An empty dictionary can be created and populated later ?

empty_dict = {}
print("Type:", type(empty_dict))
print("Dictionary =", empty_dict)

# Adding items later
empty_dict["key1"] = "value1"
print("After adding item:", empty_dict)

Type: <class 'dict'>
Dictionary = {}
After adding item: {'key1': 'value1'}

Using the dict() Function

The dict() function provides alternative ways to create dictionaries from keyword arguments or key-value pairs ?

# Using keyword arguments
employee = dict(name="Riyaansh", age=28, department="Python")
print("From keywords:", employee)

# Using list of tuples
data = dict([(1, "one"), (2, "two"), (3, "three")])
print("From tuples:", data)

# Using dict() with empty arguments
empty_dict = dict()
print("Empty dict:", empty_dict)

From keywords: {'name': 'Riyaansh', 'age': 28, 'department': 'Python'}
From tuples: {1: 'one', 2: 'two', 3: 'three'}
Empty dict: {}

Conclusion

Python dictionaries are created using curly braces {} with key-value pairs separated by colons and commas. You can also use the dict() function for more flexible creation methods. Remember that keys must be unique and immutable types.