Merge Dictionaries Effortlessly in Python: A Clean and Efficient Guide

The Annoying Way vs. The Pythonic Way

Imagine this: You’re working on a Python project, and you have two dictionaries—maybe one contains user details, and the other has their preferences. You need to combine them.

Old-school approach: You might write a loop or use .update(), which feels clunky.

Pythonic approach: You simply write {**dict1, **dict2} and smile as everything merges seamlessly.

If you’ve ever struggled with merging dictionaries in Python, this guide will show you the cleanest, most efficient ways to do it—without unnecessary code.

Why Merge Dictionaries?

Dictionaries (dict) are one of Python’s most useful data structures. They store key-value pairs, making them perfect for:

• Configuration settings
• API responses
• Data aggregation
• Combining datasets

But when you need to merge two or more dictionaries, doing it the wrong way can lead to:

• Verbose, hard-to-read code (nested loops, multiple .update() calls)
• Unintended overwrites (if keys clash)
• Reduced performance (slower execution with manual merging)

Let’s fix that.

3 Best Ways to Merge Dictionaries in Python

1. The Unpacking Operator (**) – Python 3.5+

The simplest and most elegant method:

```python
dict1 = {"name": "Alice", "age": 25}
dict2 = {"city": "New York", "age": 26}

merged_dict = {dict1, dict2}
print(merged_dict)
```

Output:
{"name": "Alice", "age": 26, "city": "New York"}

✅ Pros:
- Clean, one-liner
- No extra method calls
- Works with any number of dicts ({**dict1, **dict2, **dict3})

❌ Cons:
- If keys overlap, the last dictionary’s value wins (here, age is 26).

2. The .update() Method – Classic but Clunky

Before Python 3.5, this was the standard way:

```python
dict1 = {"name": "Alice"}
dict2 = {"city": "Boston"}

dict1.update(dict2)
print(dict1)
```

Output:
{"name": "Alice", "city": "Boston"}

✅ Pros:
- Works in older Python versions
- Modifies the original dictionary (useful for in-place updates)

❌ Cons:
- Modifies dict1 instead of creating a new dict
- Requires an extra line of code

3. The | Merge Operator – Python 3.9+

Python 3.9 introduced a dedicated merge operator:

```python
dict1 = {"a": 1, "b": 2}
dict2 = {"b": 3, "c": 4}

merged_dict = dict1 | dict2
print(merged_dict)
```

Output:
{"a": 1, "b": 3, "c": 4}

✅ Pros:
- Extremely readable (dict1 | dict2 looks intuitive)
- Works like the unpacking method (last dict wins on conflicts)

❌ Cons:
- Only available in Python 3.9+

Which Method Should You Use?

| Method | Best For | Python Version |
|----------------------|-----------------------------------|----------------|
| {**dict1, **dict2} | Clean, modern merging | 3.5+ |
| .update() | Modifying a dict in-place | All versions |
| dict1 | dict2 | Most readable syntax | 3.9+ |

Recommendation:
- If you’re on Python 3.9+, use | for clarity.
- If you’re on 3.5+, unpacking (**) is the best balance.
- If you need backward compatibility, .update() works but is less elegant.

Bonus: Handling Nested Dictionaries

What if your dictionaries have nested structures?

```python
from collections import defaultdict

def deep_merge(dict1, dict2):
result = defaultdict(dict)
for key, value in {dict1, dict2}.items():
if key in dict1 and key in dict2:
if isinstance(dict1[key], dict) and isinstance(dict2[key], dict):
result[key] = deep_merge(dict1[key], dict2[key])
else:
result[key] = dict2[key] # Override
else:
result[key] = value
return dict(result)

dict1 = {"user": {"name": "Alice", "age": 25}}
dict2 = {"user": {"age": 26, "city": "Paris"}}

print(deep_merge(dict1, dict2))
```

Output:
{"user": {"name": "Alice", "age": 26, "city": "Paris"}}

Final Thoughts

Merging dictionaries doesn’t have to be complicated. Python keeps improving, giving us cleaner ways (| operator) to write concise, efficient code.

Which method do you prefer? Do you still use .update(), or have you switched to the newer syntax? Let’s discuss in the comments! 💬

Happy coding! 🚀