Basics Of Array

Need of Arrays

Arrays address several practical programming needs:

• Efficiently store and manipulate large collections of numeric data
• Perform operations on data of the same type without repeated type checks
• Use less memory compared to lists when dealing with homogeneous data
• Interface easily with low-level languages (like C) and system-level APIs

For simple array operations, Python provides the built-in array module. For advanced numerical computations, libraries like NumPy are recommended.

Importing the Array Module

Before creating arrays, you must import the array module.

import array

# OR (alias)
import array as arr

# OR (import all functions)
from array import *

Creating an Array

Arrays are created using the array() constructor. You must specify:

1. Type code (defines the data type)
2. Initial values (as a list or iterable)

Syntax

array(typecode, [values])

Example

from array import *

vals = array('i', [5, 9, 8, 4, 2])
print(vals)

Explanation:

• 'i' → Type code for signed integers
• [5, 9, 8, 4, 2] → Initial values

All elements are stored sequentially in memory, making access and processing faster.

Type Codes in Python Arrays

Python arrays use type codes to enforce single-type storage.

Signed vs Unsigned

• Signed integers can store both positive and negative numbers.
• Unsigned integers can store only non-negative values.

from array import *

# Signed integers (allows negative values)
vals = array('i', [5, 9, -8, 4, 2])

# Unsigned integers (error if negative value used)
vals_unsigned = array('I', [5, 9, 8, 4, 2])
print(vals)

Indexing and Accessing Elements

Array elements can be accessed using index numbers, starting from 0.

vals = array('i', [5, 9, 8, 4, 2])

print(vals[0])   # 5
print(vals[3])   # 4

Get Array Length

print(len(vals))   # Output → 5

Array of Characters

vals = array('u', ['a', 'e', 'i', 'o', 'u'])
print(vals)
# Output → array('u', 'aeiou')

Traversing Arrays (Fetching Values)

There are multiple ways to fetch and display values from an array.

Using For Loop (unknown length)

for i in range(len(vals)):
    print(vals[i])

Using For Loop (with known length)

for i in range(5):
    print(vals[i])

Using Direct Iteration

for e in vals:
    print(e)

Using While Loop

i = 0
while i < len(vals):
    print(vals[i])
    i += 1

Summary

• Arrays are memory-efficient and ideal for handling numeric data.
• They provide better performance for numerical operations compared to lists.
• Arrays store only one data type, enforced through type codes.
• The array module must be explicitly imported before use.
• For advanced numerical and scientific computations, NumPy is generally the preferred option.