Stateful Sessions¶

The REPL maintains state across commands, making it perfect for interactive exploration.

How Sessions Work¶

When you switch to a language, run creates a session that persists:

Variables
Functions
Classes
Imports/requires
Global state

This state remains until you:

Switch to another language
Use :reset
Exit the REPL

Session Examples¶

Python Session¶

>>> :py
python>>> import math

python>>> x = 10

python>>> def double(n):
...     return n * 2

python>>> double(x)
20

python>>> math.pi * x
31.41592653589793

All variables and imports persist!

JavaScript Session¶

>>> :js
javascript>>> let data = []

javascript>>> data.push({name: 'Alice'})

javascript>>> data.push({name: 'Bob'})

javascript>>> data
[ { name: 'Alice' }, { name: 'Bob' } ]

Rust Session¶

>>> :rust
rust>>> let mut count = 0;

rust>>> count += 1;

rust>>> count += 1;

rust>>> count
2

Session Isolation¶

Each language has its own session:

>>> :py
python>>> x = 10

>>> :js
javascript>>> let x = 20

>>> :py
python>>> x
10  # Python's x is preserved

>>> :js
javascript>>> x
20  # JavaScript's x is preserved

Resetting Sessions¶

Clear all state:

python>>> x = 100
python>>> y = 200

python>>> :reset
session for 'python' reset

python>>> x
NameError: name 'x' is not defined

Session Persistence¶

What Persists¶

Variables
Functions
Classes
Imports
Global state

What Doesn't Persist¶

File I/O (files are closed)
Network connections
External processes

Advanced Usage¶

Building Complex State¶

python>>> # Build a data structure incrementally
python>>> users = []

python>>> users.append({'name': 'Alice', 'age': 30})

python>>> users.append({'name': 'Bob', 'age': 25})

python>>> def find_user(name):
...     return next(u for u in users if u['name'] == name)

python>>> find_user('Alice')
{'name': 'Alice', 'age': 30}

Loading Utilities¶

python>>> :load utils.py
# utils.py functions now available

python>>> :load config.py
# config.py variables now available

python>>> # Use them together
python>>> process_data(config.API_KEY)

Next Steps¶

Language-Specific Behavior → Commands Reference →