Is there a maximum value for an int in Python?
No. Python 3 integers have arbitrary precision: they grow to use as much memory as the value needs, so they never overflow. sys.maxsize is only the largest index a container can have, not the largest int. Floats, by contrast, are 64-bit and do overflow to inf.
Explain it simply
In C or Java, an int is a fixed-size box, like a 4-digit odometer that rolls back to 0000 after 9999. A Python int is more like a notebook that adds pages as the number grows. It only stops when the computer runs out of memory.
Example
big = 2 ** 100
print(big) # 1267650600228229401496703205376
print(big + 1) # 1267650600228229401496703205377
import math
print(len(str(math.factorial(100)))) # 158 digits, no overflow
import sys
print(sys.maxsize) # 9223372036854775807 on a 64-bit machine
print(float(10 ** 308) * 10) # inf (floats do overflow)The cost is speed: arithmetic on huge integers is slower than on small ones, because Python works on them digit-chunk by digit-chunk.
Since Python 3.11, converting a very long string to int (or an int to str) is limited to 4300 digits by default, as a protection against denial-of-service input. You can change it with sys.set_int_max_str_digits(). The int itself can still be larger; only the text conversion is limited.
What to say in the interview
"Python 3 ints are arbitrary precision, so there is no overflow; sys.maxsize is just the maximum container size. This is why factorial or Fibonacci problems are easy in Python. Floats are still IEEE 754 doubles and can overflow to inf."
Common mistakes
- Quoting
sys.maxsizeas the biggest possible int. - Assuming integer overflow checks from C or Java carry over to Python.