What is basestring in Python?

A base64 string is a way of encoding binary data (like images, audio, or files) into a text format. This is useful for transmitting data over mediums that are designed to handle text (such as JSON or XML) or for embedding binary data directly into web pages.

Why Base64 Encoding?

• Text-Friendly: Binary data like images cannot be included in JSON or HTML directly because they contain non-text characters. Base64 converts them into a safe, text-based format.
• Universal Support: Base64 strings can be transmitted and processed across systems and platforms without compatibility issues.

---

How Base64 Works

Base64 represents binary data as a sequence of ASCII characters. It does this by dividing the binary data into chunks of 6 bits (since ASCII uses 64 printable characters) and then mapping those chunks to a predefined set of 64 ASCII characters.

For example:

• Binary data: 01001000 01000101 01001100 01001100 01001111
• Base64 encoding: SGVMT0

---

Common Use Cases

1. Embedding Images in HTML:

   <img src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUA..."/>

1. Storing Images in JSON:

   {
       "image": "iVBORw0KGgoAAAANSUhEUgAAAAUA..."
   }

1. Encoding Files for Transmission: Base64 encoding ensures that files remain intact when transmitted over text-based protocols such as HTTP or SMTP.

---

Base64 Example in Python

import base64

# Encode a string to base64
data = "Hello, World!"
encoded = base64.b64encode(data.encode())
print(encoded)  # Output: b'SGVsbG8sIFdvcmxkIQ=='

# Decode a base64 string
decoded = base64.b64decode(encoded).decode()
print(decoded)  # Output: "Hello, World!"

---

Characteristics of Base64 Strings

1. Padding: Base64 strings often end with = or == to ensure that the encoded string length is divisible by 4.
2. Length Expansion: Base64 increases the size of the original data by approximately 33%. For example, a 3-byte binary sequence becomes 4 base64 characters.

The above is the detailed content of What is basestring in Python?. For more information, please follow other related articles on the PHP Chinese website!