The **`base64.b4()`** function in Python decodes strings or byte-like objects encoded in base64 and returns the decoded bytes.

The `base64.b64decode()` function takes `s` as the only mandatory parameter.
* `s` contains a byte-like object that is to be decoded.
* The `altchars` parameter specifies the alternative characters encoded instead of `+` or `/` characters. `altchars` is a byte-like object and must have a minimum length of 2.
* If the `validate` parameter is `False`, the function will discard all non-base64 or non-alternative characters in `s`; otherwise, it raises the `binascii.Error` exception.

>**Note**: The `base64.b64encode()` function encodes 3 bytes at a time. If the last set of bytes contains less than 3 bytes, its encoding is padded with the `=` character. One `=` character means the last set contains two bytes, and two `=` characters mean the last set contains a single byte.

# Examples
## Example 1
The following code demonstrates how to decode a byte-like object in `base64` without alternative characters.

* The program obtains the binary form of the string `pppfoo???` through the `utf-8` encoding.
* The program then encodes the bytes in base64 and displays the encoded data.
* To check the correctness of the encoding, the program decodes the encoded data using the `base64.b64decode()` function.
* The decoded form is converted from binary to string and displayed. The initial and final strings are identical, as illustrated.


import base64

#string to encode
string = 'pppfoo???'
#convert string to bytes
string_encode = string.encode('utf-8')
#ecode in base 64
encoded = base64.b64encode(string_encode)
#display encode data
print(encoded)
#decode from base 64
decoded = base64.b64decode(encoded)
#convert from bytes to string and display
print(decoded.decode('utf-8'))

## Example 2
The following program demonstrates how to decode a byte-like object in base64 with alternative characters.

* The program obtains the binary form of the string `pppfoo???` through the `utf-8` encoding.
* The program then encodes the bytes in base64 and specifies in the `altchars` argument that `/` or `+` is to be encoded with `:`.
* To check the correctness of the encoding, the program decodes the encoded data using the `base64.b64decode()` function. The `altchars` parameter is input to specify that `/` or `+` is encoded as `:`.
* The decoded form is converted from binary to strings and displayed. The initial and final strings are identical, as illustrated.

> If the program does not specify the `altchars` parameter while decoding, a `binascii.Error` exception will be thrown, as `:` does not belong to the normal base64 alphabets.


import base64

#string to encode
string = 'pppfoo???'
#convert string to bytes
string_encode = string.encode('utf-8')
#ecode in base 64
encoded = base64.b64encode(string_encode, altchars=b'-:')
#display encode data
print(encoded)
#decode from base 64
decoded = base64.b64decode(encoded,  altchars=b'-:')
#convert from bytes to string and display
print(decoded.decode('utf-8'))

> If the padding of the encoded data is incorrect, the program throws a `binascii.Error` exception.

How to use base64.b64decode() in Python

Decode base64 strings in Python using base64.b64decode(). Allows altchars for '/' and '+'. Throws exceptions for invalid input or incorrect padding.

How to use base64.b64decode() in Python

Prototype and parameters

Examples

Example 1

Example 2