sys.getsizeof

Learn to measure memory with sys.getsizeof.

What is sys.getsizeof?

sys.getsizeof(obj) returns the number of bytes an object occupies in memory. It is the fundamental tool for memory optimization.

For example sys.getsizeof([1, 2, 3]) gives the size of a list and sys.getsizeof((1, 2, 3)) of a tuple. A list uses more memory than a tuple because it is dynamic. This measurement helps determine which data structure is more efficient. In large datasets small differences can matter.

List vs tuple comparison

A list keeps extra capacity to grow; so it is larger than a tuple with the same items. You see this difference with sys.getsizeof.

For example [1, 2, 3] is about 88 bytes while (1, 2, 3) is 64 bytes. A tuple is immutable, so it needs no extra capacity. This is one reason tuples are preferred for fixed data. getsizeof gives only the container size; it does not count the items inside. For the full size you must measure each item separately.

Exercise Compare sizes with getsizeof

Import the module with import sys. Define a = [1, 2, 3] and b = (1, 2, 3). Print sys.getsizeof(a) and sys.getsizeof(b) on separate lines.

Show example solution

import sys

a = [1, 2, 3]
b = (1, 2, 3)
print(sys.getsizeof(a))
print(sys.getsizeof(b))

Test yourself

Match getsizeof concepts

sys.getsizeof

Byte size
list

Dynamic container
tuple

Immutable container
byte

Memory unit
Which uses less memory?
```
import sys
print(sys.getsizeof([1,2,3]))
print(sys.getsizeof((1,2,3)))
```
- Both equal
- List
- Tuple
- It depends
Show answer

Tuple — A tuple is immutable so it keeps no extra capacity; it uses less memory.

Complete the getsizeof call

import sys
size = sys.____([1, 2, 3])

Show answer

import sys
size = sys.getsizeof([1, 2, 3])

Next lesson: slots and tuple

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