Python str() Function

The str() function in Python is used to convert values into a string format. Whether it’s a number, a list, or an object, str() gives you the string version of it.

Syntax

str(object='', encoding='utf-8', errors='strict')

Parameters:

• object (optional) – The object you want to convert to a string.
• encoding (optional) – Only used if the object is a bytes-like object.
• errors (optional) – Specifies how to handle encoding errors.

Returns:

• A string version of the specified object.

Example 1: Converting Numbers to Strings

x = 123
print(str(x))

'123'

Example 2: Converting a List to a String

my_list = [1, 2, 3]
print(str(my_list))

'[1, 2, 3]'

Example 3: Using str() with a Float

pi = 3.14159
print(str(pi))

'3.14159'

Use Case: String Concatenation

Sometimes you want to add text and numbers together. You need to convert the number into a string first:

name = "Alice"
age = 25
print("Name: " + name + ", Age: " + str(age))

Name: Alice, Age: 25

Special Case: Encoding and Decoding Bytes

b = b"hello"
print(str(b, encoding="utf-8"))

'hello'

Common Mistakes

• Forgetting to convert before concatenation: Trying to join strings with numbers directly will cause a TypeError.
• Using str as a variable name: This overwrites the built-in str() function. Avoid this!

Interview Tip

When asked to serialize, log, or print object details in coding interviews, str() is a quick and reliable tool.

Summary

• str() converts values to string format.
• Useful in printing, concatenation, and formatting.
• Supports numbers, lists, dictionaries, and user-defined objects.

Practice Problem

Write a program that reads your name and age, and prints a greeting using str().

name = input("Enter your name: ")
age = int(input("Enter your age: "))
print("Hello " + name + "! You are " + str(age) + " years old.")