# Python Source Code Encoding

By default, Python 3 source files are treated as encoded in UTF-8. This allows you to use Unicode characters in string literals, comments, and variable names without any special declarations.

## Default Encoding

In Python 3, the default encoding is UTF-8.

```python
# This works by default in Python 3
s = "Hello world 🌍"
print(s)
```

## Declaring Encoding

If you need to use a different encoding (e.g., for legacy reasons or specific requirements), you must declare it at the top of the file. This is done using a special comment line.

The syntax is defined in PEP 263. It must match the regular expression `coding[:=]\s*([-\w.]+)`.

### Syntax

The encoding declaration must appear on the first or second line of the file.

```python
# -*- coding: encoding_name -*-
```

Or:

```python
# coding=encoding_name
```

### Examples

Using `latin-1` (ISO-8859-1):

```python
# -*- coding: latin-1 -*-

currency = "£" # In latin-1, this might be encoded differently than UTF-8
```

## Interaction with Shebang

If a script has a shebang line (e.g., `#!/usr/bin/env python3`), the encoding declaration should go on the second line.

```python
#!/usr/bin/env python3
# -*- coding: utf-8 -*-

print("Hello")
```

[[programming/python/python]]