try-except vs if-else in Python with examples

In this tutorial, we are going to compare the try-except block with if-else statements in Python and see how they can be used in our Program. As we know, if-else statements are used with conditional statements. They can be used to select a set of statements to be executed based on a condition. We can also use a try-except pair for the same. Let’s see an example.

code1 = """
x = 5
if x:
    print("x = ",x)
else:
    print("Oh No!")
    """

code2 = """
x = 5
try:
    print("x = ",x)
except:
    print("Oh No!")
    """

print("Executing code1....")
exec(code1)
print("Executing code2")
exec(code2)

Output:

Executing code1....
x = 5
Executing code2
x = 5

In the above example program, as you can see we have stored two string of Python code in variables code1 and code2. code1 implements an if-else statement whereas code2 implements a try-except statement. From the output, you can infer that everything went well and we can implement conditional statements using try-except.

Now let’s just make a little change in our program.

code1 = """
x = 5
if x:
    print("x = ",x)
else:
    print("Oh No!")
    """

code2 = """
try:
    print("y = ",y)
except NameError:
    print("Oh No!")
    """

print("Executing code1....")
exec(code1)
print("Executing code2")
exec(code2)

Output:

Executing code1....
x = 5
Executing code2
Oh No!

As you can see, here, we have not provided the value of y in the try-except block the code catches the NameError exception and prints the statements in except block. If we do not provide the value of x in if-else code, then NameError exception will be thrown. Therefore, the use of try-except is encouraged when there is a possibility of error or exceptions.

Now that we know how we can use the try-except block as a replacement of if-else, let us see which one works faster. Have a look at the below Python program.

import timeit

code1 = """
x = 5
if x:
    print("x = ",x)
else:
    print("Oh No!")
    """

code2 = """
x = 5
try:
    print("x = ",x)
except:
    print("Oh No!")
    """

codes = [code1, code2]
for code in codes:
    time_taken = timeit.timeit(stmt = code,number = 1)
    print(time_taken)

Output:

x = 5
0.00023400000000000504
x = 5
0.00013280000000000236

It is evident from the output that the try-except statement takes less time than an if-else statement.

Thank you.

Also read: Understanding timeit in Python