In Python, arrays are used to store multiple values in a single variable. While Python lists are more flexible and commonly used, Python also has a dedicated array module for cases where all items are of the same data type — offering better memory efficiency and performance.
In this article, we’ll cover:
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What arrays are and why use them
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The difference between lists and arrays
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Using the
arraymodule -
Common array operations
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Iterating, slicing, and modifying arrays
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Tips and common pitfalls
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A complete example
What is an Array?
An array is a data structure that stores a collection of items of the same data type. Arrays can be more efficient than lists when dealing with large amounts of numerical data.
Python Lists vs Arrays
| Feature | List | Array (array module) |
|---|---|---|
| Stores | Any data type | Same data type only |
| Flexibility | Very flexible | Less flexible but efficient |
| Performance | Slower for numeric operations | Faster for numeric operations |
| Memory usage | Higher | Lower |
Importing the Array Module
To use arrays in Python, you need to import the built-in array module:
import array
Creating an Array
Syntax:
array.array(typecode, initializer)
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typecode– represents the data type (e.g.,'i'for integer) -
initializer– optional list of values
Example:
import array
numbers = array.array('i', [1, 2, 3, 4])
print(numbers)
Output:
array('i', [1, 2, 3, 4])
Typecodes Table
| Typecode | C Type | Python Type | Size (bytes) |
|---|---|---|---|
'b' |
signed char | int | 1 |
'B' |
unsigned char | int | 1 |
'i' |
signed int | int | 2 or 4 |
'f' |
float | float | 4 |
'd' |
double | float | 8 |
'u' |
Unicode char | str (1 char) | 2 |
Basic Array Operations
✅ Accessing Elements
print(numbers[0]) # 1
✅ Modifying Elements
numbers[1] = 10
print(numbers) # array('i', [1, 10, 3, 4])
✅ Appending Elements
numbers.append(5)
✅ Inserting at a Position
numbers.insert(2, 99)
✅ Removing Elements
numbers.remove(3) # Removes the first occurrence of 3
✅ Popping Last Element
numbers.pop()
Iterating Through an Array
for num in numbers:
print(num)
Array Length
print(len(numbers)) # Number of elements
✂️ Slicing Arrays
print(numbers[1:4]) # Slices elements at index 1, 2, 3
Array Methods Overview
| Method | Description |
|---|---|
.append(x) |
Add an item to the end |
.insert(i, x) |
Insert at index i |
.remove(x) |
Remove first occurrence of x |
.pop([i]) |
Remove and return item at index i |
.index(x) |
Return index of first occurrence of x |
.reverse() |
Reverse array in place |
.buffer_info() |
Returns tuple (address, length) |
.count(x) |
Count occurrences of x |
.extend(iterable) |
Append elements from iterable |
Complete Example: Working with Float Array
import array
# Create array of floats
temperatures = array.array('f', [98.6, 99.4, 100.2, 97.8])
# Add a temperature
temperatures.append(98.0)
# Remove one
temperatures.remove(100.2)
# Calculate average
average = sum(temperatures) / len(temperatures)
print("Temperatures:", temperatures)
print("Average:", average)
Output:
Temperatures: array('f', [98.6, 99.4, 97.8, 98.0])
Average: 98.45
⚠️ Common Pitfalls
| Pitfall | What Happens | Fix |
|---|---|---|
| Mixing data types | Raises TypeError |
Use same type throughout |
| Using wrong typecode | Raises TypeError or OverflowError |
Refer to the typecode table |
| Treating arrays like lists blindly | Some list methods don’t exist on arrays | Use .tolist() if needed |
Importing from numpy by mistake |
Confusing built-in array with NumPy | Use import array not import numpy |
Tips and Best Practices
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✅ Use
array.arraywhen storing large numeric datasets and memory efficiency matters. -
✅ Use Python lists if you need to store mixed data types.
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✅ Convert array to list if needed using
.tolist():
num_list = numbers.tolist()
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✅ For scientific computing, use NumPy arrays, which are far more powerful than Python’s basic arrays.
What’s Next?
After understanding arrays, you might want to explore:
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Lists vs Arrays in-depth
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NumPy arrays for advanced numerical work
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Memory profiling to compare performance
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Using arrays in binary file I/O and data streams
Tips and Tricks
What is pass in Python?
Python | Pass Statement
The pass statement is used as a placeholder for future code. It represents a null operation in Python. It is generally used for the purpose of filling up empty blocks of code which may execute during runtime but has yet to be written.
def myfunction():
pass
How can you generate random numbers?
Python | Generate random numbers
Python provides a module called random using which we can generate random numbers. e.g: print(random.random())
We have to import a random module and call the random() method as shown below:
import random
print(random.random())
The random() method generates float values lying between 0 and 1 randomly.
To generate customized random numbers between specified ranges, we can use the randrange() method
Syntax: randrange(beginning, end, step)
import random
print(random.randrange(5,100,2))
What is lambda in Python?
Python | Lambda function
A lambda function is a small anonymous function. This function can have any number of parameters but, can have just one statement.
Syntex:
lambda arguments : expression
a = lambda x,y : x+y
print(a(5, 6))
It also provides a nice way to write closures. With that power, you can do things like this.
def adder(x):
return lambda y: x + y
add5 = adder(5)
add5(1) #6
As you can see from the snippet of Python, the function adder takes in an argument x and returns an anonymous function, or lambda, that takes another argument y. That anonymous function allows you to create functions from functions. This is a simple example, but it should convey the power lambdas and closures have.
What is swapcase() function in the Python?
Python | swapcase() Function
It is a string's function that converts all uppercase characters into lowercase and vice versa. It automatically ignores all the non-alphabetic characters.
string = "IT IS IN LOWERCASE."
print(string.swapcase())
How to remove whitespaces from a string in Python?
Python | strip() Function | Remove whitespaces from a string
To remove the whitespaces and trailing spaces from the string, Python provides a strip([str]) built-in function. This function returns a copy of the string after removing whitespaces if present. Otherwise returns the original string.
string = " Python "
print(string.strip())
What is the usage of enumerate() function in Python?
Python | enumerate() Function
The enumerate() function is used to iterate through the sequence and retrieve the index position and its corresponding value at the same time.
lst = ["A","B","C"]
print (list(enumerate(lst)))
#[(0, 'A'), (1, 'B'), (2, 'C')]
Can you explain the filter(), map(), and reduce() functions?
Python | filter(), map(), and reduce() Functions
- filter() function accepts two arguments, a function and an iterable, where each element of the iterable is filtered through the function to test if the item is accepted or not.
>>> set(filter(lambda x:x>4, range(7))) # {5, 6}
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map() function calls the specified function for each item of an iterable and returns a list of result
>>> set(map(lambda x:x**3, range(7))) # {0, 1, 64, 8, 216, 27, 125}
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reduce() function reduces a sequence pair-wise, repeatedly until we arrive at a single value..
>>> reduce(lambda x,y:y-x, [1,2,3,4,5]) # 3Let’s understand this:
2-1=1
3-1=2
4-2=2
5-2=3Hence, 3.
What is a namedtuple?
Python | namedtuple
A namedtuple will let us access a tuple’s elements using a name/label. We use the function namedtuple() for this, and import it from collections.
>>> from collections import namedtuple
#format
>>> result=namedtuple('result','Physics Chemistry Maths')
#declaring the tuple
>>> Chris=result(Physics=86,Chemistry=92,Maths=80)
>>> Chris.Chemistry
# 92
Write a code to add the values of same keys in two different dictionaries and return a new dictionary.
We can use the Counter method from the collections module
from collections import Counter
dict1 = {'a': 5, 'b': 3, 'c': 2}
dict2 = {'a': 2, 'b': 4, 'c': 3}
new_dict = Counter(dict1) + Counter(dict2)
print(new_dict)
# Print: Counter({'a': 7, 'b': 7, 'c': 5})
Python In-place swapping of two numbers
Python | In-place swapping of two numbers
>>> a, b = 10, 20
>>> print(a, b)
10 20
>>> a, b = b, a
>>> print(a, b)
20 10
Reversing a String in Python
Python | Reversing a String
>>> x = 'PythonWorld'
>>> print(x[: : -1])
dlroWnohtyP
Python join all items of a list to convert into a single string
Python | Join all items of a list to convert into a single string
>>> x = ["Python", "Online", "Training"]
>>> print(" ".join(x))
Python Online Training
python return multiple values from functions
Python | Return multiple values from functions
>>> def A():
return 2, 3, 4
>>> a, b, c = A()
>>> print(a, b, c)
2 3 4
Python Print String N times
Python | Print String N times
>>> s = 'Python'
>>> n = 5
>>> print(s * n)
PythonPythonPythonPythonPython
Python check the memory usage of an object
Python | Check the memory usage of an object
>>> import sys
>>> x = 100
>>> print(sys.getsizeof(x))
28
