What's the difference between () vs [] vs {}?

Question

What\'s the difference between () vs [] vs {} in Python?
They\'re collections? How can I tell when to use which?

Answer 1

() - tuple

A tuple is a sequence of items that can't be changed (immutable).

[] - list

A list is a sequence of items that can be changed (mutable).

{} - dictionary or set

A dictionary is a list of key-value pairs, with unique keys (mutable). From Python 2.7/3.1, {} can also represent a set of unique values (mutable).

Answer 2

() - tuple
[] - list
{} - dictionary

All Python tutorials should cover this. Here is a good place to start.

Answer 3

In addition to the tuple, list and dict given by the other answers, {} also denotes a set literal in python 2.7 and python 3.1. (This makes sense because set elements act like the keys of a dict).

Answer 4

• () is a tuple: An immutable collection of values, usually (but not necessarily) of different types.
• [] is a list: A mutable collection of values, usually (but not necessarily) of the same type.
• {} is a dict: Use a dictionary for key value pairs.

For the difference between lists and tuples see here. See also:

• Python Tuples are Not Just Constant Lists