How many key-value pairs can a Python dictionary contain?

Theoretically, the number of key-value pairs in a Python dictionary is limited only by the available system RAM.

Each pair consumes a certain amount of memory, and when memory runs out, Python cannot add new elements, leading to a MemoryError.

In practice, on 64-bit systems, available memory can reach terabytes, allowing the creation of dictionaries with billions of elements. However, as the dictionary size grows, operations like search, insert, and delete may become less efficient due to increased collision resolution time in the hash table underlying the dictionary implementation.

# Example of creating a large dictionary (may consume a lot of memory and time)
try:
    large_dict = {i: i for i in range(10**9)}  # Attempt to create a dictionary with a billion elements
    print(len(large_dict))
except MemoryError:
    print("Not enough memory to create such a large dictionary.")

# Maximum number of elements that can be stored in a dictionary (sys.maxsize)
# sys.maxsize represents the maximum possible value for an integer in Python
import sys
print(f"Theoretical limit: {sys.maxsize} elements.")

Dependency table:

Factor	Impact on maximum dictionary size
RAM capacity	Main limitation
System architecture	Affects available memory
Size of keys and values	Affects memory consumption per pair
Hashing efficiency	Affects performance at large sizes