How many parentheses can Python handle?

During my office hours today I was asked whether “an extra pair of parentheses” would do any harm to the execution of a Python program. In the case at hand the answer was “no”, but I suspected there might be actually be a limit on nested parentheses depth.

Using the following Python script (which leverages the ability of the interpreter to evaluate expressions at runtime via eval), we can determine the answer is 200. For any greater depth one receives a SyntaxError: too many nested parentheses.

from sys import maxsize

def parens_expr(N):
   s = '('*N + '1 + 2' + ')'*N 
   return eval(s)

max_depth = 0
for i in range(maxsize):
        max_depth = i

print(f'maximal parentheses depth: {max_depth}')
parens_expr(max_depth + 1)  # to demonstrate failure

A fun quote

posted 2023-10-10