How to fix Python TypeError: lru_cache() got an unexpected keyword argument 'max_size

Problem:

In Python, you’re using code such as

from functools import lru_cache

@lru_cache(max_size=128)
def myfunc(arg: str):
   # ...
   return arg + "x"

but you see an error message such as

Traceback (most recent call last):
  File "/dev/shm/test.py", line 3, in <module>
    @lru_cache(max_size=128)
TypeError: lru_cache() got an unexpected keyword argument 'max_size'

Solution

You’ve mis-spelled the argument to @lru_cache: You wrote max_size with underscore whereas it actually is maxsize without underscore.