sys.getsizeof
- Python course
- Expert
- Lesson 39/47
- 5 min
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.
Practice 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.
Starter code
# create a list and a tuple
# print their sizesSample solution
import sys
a = [1, 2, 3]
b = (1, 2, 3)
print(sys.getsizeof(a))
print(sys.getsizeof(b))Expected output
88 64
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Match getsizeof concepts
| Term | Meaning |
|---|---|
sys.getsizeof |
Byte size |
list |
Dynamic container |
tuple |
Immutable container |
byte |
Memory unit |
2 Which uses less memory?
import sys
print(sys.getsizeof([1,2,3]))
print(sys.getsizeof((1,2,3)))- Both equal
- List
- Tuple Correct answer
- It depends
Explanation: A tuple is immutable so it keeps no extra capacity; it uses less memory.
3 Complete the getsizeof call
import sys
size = sys.____([1, 2, 3])import sys
size = sys.getsizeof([1, 2, 3])Explanation: sys.getsizeof(obj) returns the byte size.