All About python dictionary

# Nested dictionary representing students in a classroom

classroom = {

    "student1": {

        "name": "Alice",

        "age": 16,

        "subjects": ["Math", "Science", "English"],

        "grades": {"Math": 90, "Science": 85, "English": 88}

    },

    "student2": {

        "name": "Bob",

        "age": 17,

        "subjects": ["History", "Art", "Physics"],

        "grades": {"History": 78, "Art": 92, "Physics": 88}

    }

}

new_dict = {"student3": {

        "name": "Charlie",

        "age": 16,

        "subjects": ["Biology", "Chemistry", "Math"],

        "grades": {"Biology": 82, "Chemistry": 89, "Math": 95}

    }

}

# update dict

classroom.update(new_dict)

print(classroom) # it will add the new_dict in classroom

# Loop Through dict key and value

for k, v in classroom.items():

    print(k, v) # it will get all keys and values from classroom dictionary

student1 = classroom.get("student1")

print(student1) # we will get the studen1

student1_name = student1['name']

print(student1_name)

student2 = classroom.get("student2")

student2_name = student2['name'] = "Christopher"

print(student2_name)

print(classroom)

# Dictionary Comprehensions

squares = {x : x**2 for x in range(1, 11)}

print(squares)

# Merge Dictionaries

# Define two dictionaries with overlapping keys

dict1 = {

    "a": 1,

    "b": 2,

    "c": 3

}

dict2 = {

    "b": 20,  # Overlapping key

    "c": 30,  # Overlapping key

    "d": 4

}

# Merge dictionaries, keeping values from dict2 in case of conflicts

merged_dict = dict1.copy()  # Copy dict1 to preserve original

merged_dict.update(dict2)    # Update with dict2 (overwriting conflicts)

# Print the merged dictionary

print(merged_dict)

# Altenate Method

merged_dict = dict1 | dict2

print(merged_dict)

# Update Alice's age

classroom["student1"]["age"] = 17

# Add a new subject for Bob

classroom["student2"]["subjects"].append("Chemistry")

print(classroom)

# Removing Items

# Using del to remove student1

del classroom["student1"]

# Using pop() to remove student2 and return its value

student2 = classroom.pop("student2")

# Using popitem() to remove the last inserted key-value pair

last_item = classroom.popitem()

print(classroom)

using jmespath to play with dictionary:

Basic JMESPath Syntax

Here’s how you can use JMESPath to select values from a dictionary:

1. Select a Specific Key:

   • Use the key name directly to select its value.

2. Nested Selection:

   • Use dots (.) to navigate through nested dictionaries.

3. Wildcards:

   • Use * to select all elements in a list or dictionary.

4. Filtering:

• Use [?expression] to filter elements based on a condition.

import jmespath

data = {

    "classroom": {

        "students": [

            {"name": "Alice", "age": 16, "grades": {"Math": 90, "Science": 85}},

            {"name": "Bob", "age": 17, "grades": {"Math": 78, "Science": 92}},

            {"name": "Charlie", "age": 16, "grades": {"Math": 88, "Science": 84}}

        ],

        "teacher": {

            "name": "Mr. Smith",

            "subject": "Math"

        }

    }

}

Select the Teacher's Name:

expression = "classroom.teacher.name"

result = jmespath.search(expression, data)

print(result)  # Output: Mr. Smith

Select All Student Names:

expression = "classroom.students[*].name"

result = jmespath.search(expression, data)

print(result)  # Output: ['Alice', 'Bob', 'Charlie']

Select Grades for All Students:

expression = "classroom.students[*].grades"

result = jmespath.search(expression, data)

print(result)  # Output: [{'Math': 90, 'Science': 85}, {'Math': 78, 'Science': 92}, {'Math': 88, 'Science': 84}]

Select Students Aged 16:

expression = "classroom.students[?age==`16`]"

result = jmespath.search(expression, data)

print(result)  # Output: [{'name': 'Alice', 'age': 16, 'grades': {'Math': 90, 'Science': 85}}, {'name': 'Charlie', 'age': 16, 'grades': {'Math': 88, 'Science': 84}}]

Select Math Grades for All Students:

expression = "classroom.students[*].grades.Math"

result = jmespath.search(expression, data)

print(result)  # Output: [90, 78, 88]

Select the First Student's Name:

expression = "classroom.students[0].name"

result = jmespath.search(expression, data)

print(result)  # Output: Alice

Select Students with Math Grades Above 85:

expression = "classroom.students[?grades.Math > `85`]"

result = jmespath.search(expression, data)

print(result)  # Output: [{'name': 'Alice', 'age': 16, 'grades': {'Math': 90, 'Science': 85}}, {'name': 'Charlie', 'age': 16, 'grades': {'Math': 88, 'Science': 84}}]

Dictionary to JSON:

import json

my_dict = {"name": "Alice", "age": 25}

json_string = json.dumps(my_dict)

print(json_string)  # Output: {"name": "Alice", "age": 25}

Dictionary from JSON:

import json

json_string = '{"name": "Alice", "age": 25}'

my_dict = json.loads(json_string)

print(my_dict)  # Output: {"name": "Alice", "age": 25}