Stryg for at vise menuen

sys.getsizeof() is the most direct tool for measuring how much memory a single Python object occupies. Understanding what it measures – and what it does not – prevents common misinterpretations and helps you accurately compare the memory cost of different data representations.

What `sys.getsizeof()` Measures

sys.getsizeof() returns the size of the object itself in bytes – the object header, internal pointers, and any inline data. It does not include the size of objects the target object references:


              1234567891011
            
import sys

# getsizeof measures the container, not its contents
price_list = [1500.0, 2300.0, 4100.0, 750.0]
print(sys.getsizeof(price_list))       # ~120 bytes – list structure + 4 pointers

single_float = 1500.0
print(sys.getsizeof(single_float))     # 24 bytes – one float object

# The list does NOT include the floats it points to
print(sys.getsizeof(price_list) + 4 * sys.getsizeof(1500.0))  # Closer to true total

Total Size Including References

To measure the true memory footprint of a nested structure, recursively sum all referenced objects:


              12345678910111213141516171819202122232425262728
            
import sys

def total_size(obj, seen=None):
    """Recursively calculate total memory of an object and all it references."""
    size = sys.getsizeof(obj)
    if seen is None:
        seen = set()
    obj_id = id(obj)
    if obj_id in seen:
        return 0
    seen.add(obj_id)

    if isinstance(obj, dict):
        size += sum(total_size(key, seen) + total_size(value, seen) for key, value in obj.items())
    elif isinstance(obj, (list, tuple, set, frozenset)):
        size += sum(total_size(item, seen) for item in obj)

    return size

# Comparing shallow vs total size
transaction_record = {
    "id": "TX_001",
    "amount": 4500.0,
    "tags": ["urgent", "international", "flagged"],
}

print(f"getsizeof only:   {sys.getsizeof(transaction_record)} bytes")
print(f"Total recursive:  {total_size(transaction_record)} bytes")

Comparing Common Structures


              1234567891011
            
import sys
import array
from collections import deque

items = list(range(1000))

print(f"list of 1000 ints:      {sys.getsizeof(items)} bytes (container only)")
print(f"tuple of 1000 ints:     {sys.getsizeof(tuple(items))} bytes")
print(f"set of 1000 ints:       {sys.getsizeof(set(items))} bytes")
print(f"array.array of 1000:    {sys.getsizeof(array.array('i', items))} bytes")
print(f"deque of 1000 ints:     {sys.getsizeof(deque(items))} bytes")

array.array stores values inline – sys.getsizeof() reflects the actual data size. For list, tuple, and set, the reported size is the container overhead plus pointers – the integer objects themselves are counted separately.

String Size Breakdown

Strings in Python carry encoding overhead. The size scales with content:


              1234567
            
import sys

print(sys.getsizeof(""))           # 49 bytes – empty string overhead
print(sys.getsizeof("a"))          # 50 bytes – one ASCII character
print(sys.getsizeof("hello"))      # 54 bytes – 5 ASCII characters
print(sys.getsizeof("héllo"))      # Larger – non-ASCII forces UCS-2 or UCS-4 encoding
print(sys.getsizeof("hello" * 100))  # ~549 bytes – 500 characters

Practical Size Reference

Var alt klart?

Tak for dine kommentarer!

Sektion 4. Kapitel 4

Spørg AI

Spørg om hvad som helst eller prøv et af de foreslåede spørgsmål for at starte vores chat

sys.getsizeof() and Object Size Inspection

What `sys.getsizeof()` Measures


              1234567891011
            
import sys

# getsizeof measures the container, not its contents
price_list = [1500.0, 2300.0, 4100.0, 750.0]
print(sys.getsizeof(price_list))       # ~120 bytes – list structure + 4 pointers

single_float = 1500.0
print(sys.getsizeof(single_float))     # 24 bytes – one float object

# The list does NOT include the floats it points to
print(sys.getsizeof(price_list) + 4 * sys.getsizeof(1500.0))  # Closer to true total

Total Size Including References

To measure the true memory footprint of a nested structure, recursively sum all referenced objects:


              12345678910111213141516171819202122232425262728
            
import sys

def total_size(obj, seen=None):
    """Recursively calculate total memory of an object and all it references."""
    size = sys.getsizeof(obj)
    if seen is None:
        seen = set()
    obj_id = id(obj)
    if obj_id in seen:
        return 0
    seen.add(obj_id)

    if isinstance(obj, dict):
        size += sum(total_size(key, seen) + total_size(value, seen) for key, value in obj.items())
    elif isinstance(obj, (list, tuple, set, frozenset)):
        size += sum(total_size(item, seen) for item in obj)

    return size

# Comparing shallow vs total size
transaction_record = {
    "id": "TX_001",
    "amount": 4500.0,
    "tags": ["urgent", "international", "flagged"],
}

print(f"getsizeof only:   {sys.getsizeof(transaction_record)} bytes")
print(f"Total recursive:  {total_size(transaction_record)} bytes")

Comparing Common Structures


              1234567891011
            
import sys
import array
from collections import deque

items = list(range(1000))

print(f"list of 1000 ints:      {sys.getsizeof(items)} bytes (container only)")
print(f"tuple of 1000 ints:     {sys.getsizeof(tuple(items))} bytes")
print(f"set of 1000 ints:       {sys.getsizeof(set(items))} bytes")
print(f"array.array of 1000:    {sys.getsizeof(array.array('i', items))} bytes")
print(f"deque of 1000 ints:     {sys.getsizeof(deque(items))} bytes")

String Size Breakdown

Strings in Python carry encoding overhead. The size scales with content:


              1234567
            
import sys

print(sys.getsizeof(""))           # 49 bytes – empty string overhead
print(sys.getsizeof("a"))          # 50 bytes – one ASCII character
print(sys.getsizeof("hello"))      # 54 bytes – 5 ASCII characters
print(sys.getsizeof("héllo"))      # Larger – non-ASCII forces UCS-2 or UCS-4 encoding
print(sys.getsizeof("hello" * 100))  # ~549 bytes – 500 characters

Practical Size Reference

Var alt klart?

Tak for dine kommentarer!

Sektion 4. Kapitel 4

sys.getsizeof() and Object Size Inspection

What sys.getsizeof() Measures

Total Size Including References

Comparing Common Structures

String Size Breakdown

Practical Size Reference

sys.getsizeof() and Object Size Inspection

What sys.getsizeof() Measures

Total Size Including References

Comparing Common Structures

String Size Breakdown

Practical Size Reference

What `sys.getsizeof()` Measures

What `sys.getsizeof()` Measures