Python – Copy Dictionaries

1. What Does “Copy Dictionary” Mean?

Copying a dictionary means creating a new dictionary with the same data.

This is useful when:

  • You want to change one dictionary

  • But keep the original dictionary safe

2. Why Copying is Important

If you don’t copy correctly, both dictionaries may change together 😟

Example (Problem)

dict1 = {"a": 1, "b": 2}
dict2 = dict1

dict2["c"] = 3

print(dict1)
print(dict2)

👉 Both dictionaries change because they point to the same object.

3. Correct Way to Copy a Dictionary

Method 1: Using copy() (Best Way)

Example

dict1 = {"a": 1, "b": 2}
dict2 = dict1.copy()

dict2["c"] = 3

print(dict1)
print(dict2)

4. Method 2: Using dict() Function

Example

student = {"name": "Amit", "age": 20}

student_copy = dict(student)
print(student_copy)

5. Copy Dictionary Using Loop

Example

original = {"x": 10, "y": 20}
new_dict = {}

for key, value in original.items():
new_dict[key] = value

print(new_dict)

6. Shallow Copy (Simple Explanation)

All above methods create a shallow copy.

This is fine for simple dictionaries.

7. Common Beginner Mistakes

❌ Using = Instead of Copy

new_dict = old_dict

❌ This does NOT create a copy.

✔ Correct

new_dict = old_dict.copy()

8. Simple Practice Examples

Example 1: Copy and Change

product = {"name": "Mobile", "price": 15000}

backup = product.copy()
backup["price"] = 14000

print(product)
print(backup)

Example 2: Copy Student Data

student = {"name": "Ravi", "marks": 80}
student2 = dict(student)

print(student2)

Example 3: Safe Backup

settings = {"theme": "dark", "font": "small"}
settings_backup = settings.copy()

print(settings_backup)

9. Summary (Copy Dictionaries)

✔ Use copy() to copy dictionary
dict() also works
✔ Never use = for copying
✔ Copy keeps original safe

📘 Perfect for Beginner eBook

This chapter is ideal for:

  • Python beginner books

  • School & college students

  • Self-learners

If you want next, I can write:

  • Nested Dictionaries

  • Dictionary Methods

  • Dictionary Exercises

  • Mini Python Projects

Just tell me 😊

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