Valid Expression Evaluator – Detailed Version vs One Liner
For Long Version:
Let's dive into a powerful Python concept—using the eval() function to dynamically evaluate expressions. In this problem, you are given a single line string representing a Python expression. Your task is to evaluate this expression using eval() and print the result, but only if eval() returns a value (i.e., not when the expression already produces output on its own).
Consider the following points:
Input Handling:
The input is a single line containing a Python expression.
Use input().strip() to remove any trailing or leading whitespace.
Using eval():
The eval() function takes a string and evaluates it as a Python expression.
For example, if the input is "9 + 5", eval() will return 14.
If the expression itself is a print statement (like print(2 + 3)), eval() will execute the print function (outputting 5) and return None.
Conditional Output:
To avoid printing extra output when the expression already prints a result (i.e., when eval() returns None), we check the result.
If the evaluated result is not None, we print the result.
This solution demonstrates the flexibility and risk of using eval() for dynamic code execution while managing output appropriately.
Code (Detailed Version):
def solve():
Read the input expression and strip any extra whitespace
expr = input().strip()
Evaluate the expression using eval()
result = eval(expr)
If eval returns a value (i.e., result is not None), print it.
if result is not None:
print(result)
if _name_ == '__main__':
solve()
For One-Liner Solution:
This one-liner solution provides a concise implementation to evaluate a Python expression and print the result when applicable. It:
Reads the input string representing a Python expression.
Evaluates the expression using eval().
Prints the result if eval() produces a non-None value (useful when the input is not a print statement).
This compact approach is ideal for competitive programming and interviews, showcasing Python’s ability to handle dynamic execution in just a few lines of code.
Code (One-Liner Version):
def solve():
expr = input().strip(); result = eval(expr); print(result) if result is not None else None
if _name_ == '__main__':
solve()