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 = 3 result = 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 = 5 print ( eval ( 'x == 4' )) x = None print ( 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 tuple chars = ( 'a' , 'b' , 'c' ) print ( "'d' in chars tuple?" , eval ( "'d' in chars" )) # check if number is greater or lesser num = 100 print (num, "> 50?" , eval ( 'num > 50' )) # checking if number is even num = 20 print (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.