Python Strings decode() method

The decode() method in Python is used to convert encoded text back into its original string format. It works as the opposite of encode() method, which converts a string into a specific encoding format. For example, let's try to encode and decode a simple text message:

s = "Geeks for Geeks"

e = s.encode('utf-8')
print("Encoded text:", e)
print(type(e))

d = e.decode('utf-8')
print(type(d))
print("Decoded text:", d)

Encoded text: b'Geeks for Geeks'
<class 'bytes'>
<class 'str'>
Decoded text: Geeks for Geeks

Explanation:

• s.encode('ut-8') encodes the text into bytes format.
• e.decode('utf-8') decodes the encoded text back to normal unicode format.

Syntax

encoded_string.decode(encoding, errors)

Parameters:

1. encoding: The encoding format used for decoding (e.g., 'utf-8', 'ascii').

2. errors (Optional): Specifies how to handle errors during decoding:

• 'strict' (default): Raises an error for invalid characters.
• 'ignore': Ignores errors and proceeds.
• 'replace': Replaces invalid characters with a placeholder.

Return Type: Returns the original string after decoding.

Working of the Python Decode() Method

The following flowchart shows the working of Python decoding:

Examples of decode() method:

Example 1: Basic Encoding and Decoding

Encoding converts a string into bytes, and decode() brings it back to its original form.

t = "Hello, Python!"

# Encoding the string into UTF-8
e_t = t.encode('utf-8')
print("Encoded:", e_t)

# Decoding back to original
d_t = e_t.decode('utf-8')
print("Decoded:", d_t)

Encoded: b'Hello, Python!'
Decoded: Hello, Python!

Explanation:

• encode('utf-8') converts the string into bytes format.
• decode('utf-8') restores the original string.

Example 2: Handling Decoding Errors

Sometimes, decoding fails due to incompatible characters. Let's see how different error-handling modes work:

# Encoding with ASCII (supports only basic English characters)
s = "Café"

# Encoding the text in ASCII
enc = s.encode('ascii', errors='replace')

# Decoding with strict mode (raises error)
try:
    print(enc.decode('ascii', errors='strict'))
except UnicodeDecodeError as e:
    print("Decoding Error:", e)

# Decoding with ignore mode (ignores errors)
print("Ignored Decoding:", enc.decode('ascii', errors='ignore'))

# Decoding with replace mode (replaces errors)
print("Replaced Decoding:", enc.decode('ascii', errors='replace'))

Caf?
Ignored Decoding: Caf?
Replaced Decoding: Caf?

Explanation:

• strict mode raises an error when an unsupported character (é) is found.
• ignore mode removes unsupported characters (é).
• replace mode replaces unsupported characters with a placeholder (?).

Example 3: Real-World Use Case (Password Encoding & Decoding)

Encoding and decoding help secure sensitive data like passwords. Here’s a simple demonstration.

import base64

# User credentials
user = "user1"
passw = "secure@123"

# Encoding password
enc_pass = base64.b64encode(passw.encode('utf-8')).decode('utf-8')
print("Encoded Password:", enc_pass)

# Decoding password for verification
dec_pass = base64.b64decode(enc_pass).decode('utf-8')
print("Decoded Password:", dec_pass)

# Login verification
e_pass = "secure@123"
if e_pass == dec_pass:
    print("Login Successful!")
else:
    print("Wrong Password!")

Encoded Password: c2VjdXJlQDEyMw==
Decoded Password: secure@123
Login Successful!

Explanation:

• The password is encoded in Base64 to ensure safe storage.
• It is later decoded to verify the login.

Common Use Cases:

• Helps retrieve the original text from an encoded format.
• Essential for handling different character encodings like UTF-8, ASCII, etc.
• Useful in data transmission, security applications, and text processing.

How to use decode in Python 3?

In Python 3, the decode method is used to convert a bytes object into a str (string) object by decoding it from a specific encoding.

Example:

# Define a bytes object
bytes_obj = b'Hello, world!'

# Decode bytes object to string using UTF-8 encoding
string_obj = bytes_obj.decode('utf-8')

print(string_obj)  # Output: Hello, world!

Here, decode('utf-8') converts the bytes object from UTF-8 encoding to a string.

What does .decode('utf-8') do?

The .decode('utf-8') method converts a bytes object into a str object using the UTF-8 encoding. UTF-8 is a variable-width character encoding used for text.

Example:

# Define a bytes object with UTF-8 encoding
bytes_obj = b'\xe2\x9c\x94'

# Decode bytes object to string
string_obj = bytes_obj.decode('utf-8')

print(string_obj)  # Output: ✓

What is string decoding?

String decoding is the process of converting encoded bytes back into a string. It interprets bytes according to a specified character encoding to produce a readable string.

Example:

# Define a bytes object
bytes_obj = b'Hello'

# Decode bytes object to string
string_obj = bytes_obj.decode('utf-8')

print(string_obj)  # Output: Hello

What is an example of decode?

Here’s a basic example of how to use the decode method with a bytes object:

Example:

# Define a bytes object
bytes_data = b'Hello, Python!'

# Decode bytes object to string using UTF-8 encoding
text = bytes_data.decode('utf-8')

print(text)  # Output: Hello, Python!

What is encode() in Python?

The encode() method is used to convert a string into a bytes object using a specific encoding. This is the reverse of decode().

Example:

# Define a string
text = 'Hello, world!'

# Encode string to bytes using UTF-8 encoding
bytes_obj = text.encode('utf-8')

print(bytes_obj)  # Output: b'Hello, world!'

Additional Example of encode():

# Define a string
text = 'Hello, Python!'

# Encode string to bytes
bytes_data = text.encode('utf-8')

print(bytes_data)  # Output: b'Hello, Python!'