In Python, arrays are used to store multiple values of the same data type. Sometimes, you need to combine two or more arrays into a single array. This process is called joining arrays.
Python provides several ways to join arrays such as using +, extend(), loops, and manual methods.
In this tutorial, you will learn all methods to join arrays in Python with clear examples.
Creating Arrays
We use Python’s array module.
import array as arr
array1 = arr.array('i', [10, 20, 30])
array2 = arr.array('i', [40, 50, 60])
print(array1)
print(array2)1. Join Arrays Using Loop
You can manually join arrays using a loop.
Example
for item in array2:
array1.append(item)
print(array1)Output
array('i', [10, 20, 30, 40, 50, 60])Explanation
- Each element from array2 is added to array1
- Simple but manual method
2. Join Arrays Using + Operator (Convert to List Method)
Python arrays do not directly support +, so we convert them.
Example
joined = arr.array('i', list(array1) + list(array2))
print(joined)Output
array('i', [10, 20, 30, 40, 50, 60])3. Join Arrays Using extend() (Recommended)
The extend() method is the easiest way to join arrays.
Example
array1.extend(array2)
print(array1)Output
array('i', [10, 20, 30, 40, 50, 60])Explanation
- Adds all elements of array2 into array1
- Efficient and fast
4. Join Arrays Using List Conversion
You can convert arrays to lists and then back.
Example
joined = arr.array('i', list(array1) + list(array2))
print(joined)Output
array('i', [10, 20, 30, 40, 50, 60])5. Join Multiple Arrays
You can join more than two arrays.
Example
array3 = arr.array('i', [70, 80])
joined = arr.array('i', list(array1) + list(array2) + list(array3))
print(joined)Output
array('i', [10, 20, 30, 40, 50, 60, 70, 80])6. Join Arrays Using Loop (Multiple Arrays)
Example
arrays = [array1, array2]
result = arr.array('i')
for a in arrays:
for item in a:
result.append(item)
print(result)Real-World Example: Student Marks Merge
import array as arr
class1 = arr.array('i', [85, 90, 78])
class2 = arr.array('i', [88, 92, 80])
all_marks = arr.array('i')
all_marks.extend(class1)
all_marks.extend(class2)
print(all_marks)Real-World Example: Product Inventory Merge
import array as arr
warehouse1 = arr.array('i', [101, 102, 103])
warehouse2 = arr.array('i', [104, 105, 106])
combined = arr.array('i')
for item in warehouse1:
combined.append(item)
for item in warehouse2:
combined.append(item)
print(combined)Join Methods Comparison
| Method | Type | Description |
|---|---|---|
| extend() | Best | Fast and simple |
| loop | Manual | Educational |
| + operator | List-based | Requires conversion |
| list() | Flexible | Easy merging |
Common Mistakes
Mistake 1: Using + directly on arrays
❌ Wrong:
array1 + array2✔ Arrays require conversion
Mistake 2: Forgetting extend()
array1.extend(array2)✔ Best and recommended method
Mistake 3: Mixing data types
arr.array('i', [10, "hello"])✔ Arrays must have same type
Safe Join Example
joined = arr.array('i', list(array1) + list(array2))Array Join Methods Summary
| Method | Use |
| extend() | Best method |
| loop | Custom control |
| list + list | Flexible |
| multiple extend() | Clean merging |
Practice Exercise 1
Join two arrays using extend().
Practice Exercise 2
Join three arrays into one.
Conclusion
Joining arrays in Python is simple and very useful for combining datasets.
You learned:
- Different ways to join arrays
- Best method using
extend() - Loop-based and conversion methods
- Real-world use cases
Mastering array joining is essential for data processing, analytics, and real-world applications.
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