Evaluating Expressions using Python’s eval()
Evaluate Mathematical Expressions in Python
Evaluating a mathematical expression using the value of the variable x.
Python3
expression = 'x*(x+1)*(x+2)'print(expression)x = 3result = eval(expression)print(result) |
Output:
x*(x+1)*(x+2)
60
Evaluate Boolean Expressions in Python
Here the eval statement x == 4 will evaluate to False because the value of x is 5, which is not equal to 4. In the second eval statement, x is None will evaluate to True because the value of x is None, and is None checks for object identity, not value equality.
Python3
x = 5print(eval('x == 4'))x = Noneprint(eval('x is None')) |
Output:
False
True
Evaluate Conditional Expressions in Python
We can also evaluate condition checking on the Python eval() function.
Python3
# check if element in tuplechars = ('a', 'b', 'c')print("'d' in chars tuple?", eval("'d' in chars"))# check if number is greater or lessernum = 100print(num, "> 50?", eval('num > 50'))# checking if number is evennum = 20print(num, "is even?", eval('num % 2 == 0')) |
Output:
'd' in chars tuple? False
100 > 50? True
20 is even? True
eval in Python
Python eval() function parse the expression argument and evaluate it as a Python expression and runs Python expression (code) within the program.