Python String to Int, Int to String

If you read our previous tutorials, you may notice that at some time we used this conversion. Actually, this is necessary in many cases. For example, you are reading some data from a file, then it will be in String format and you will have to convert String to an int. Now, we will go straight to the code. If you want to convert a number that is represented in the string to int, you have to use int() function to do so. See the following example:

num = '123'  # string data

# print the type

print('Type of num is :', type(num))

# convert using int()

num = int(num)

# print the type again

print('Now, type of num is :', type(num))

The output of the following code will be

Type of num is : <class 'str'>
Now, type of num is : <class 'int'>

If the string you want to convert into int belongs to different number base other that base 10, you can specify the base for conversion. But remember that the output integer is always in base 10. Another thing you need to remember is that the given base must be in between 2 to 36. See the following example to understand the conversion of string to int with the base argument.

num = '123'
# print the original string
print('The original string :', num)

# considering '123' be in base 10, convert it to base 10

print('Base 10 to base 10:', int(num))

# considering '123' be in base 8, convert it to base 10

print('Base 8 to base 10 :', int(num, base=8))

# considering '123' be in base 6, convert it to base 10

print('Base 6 to base 10 :', int(num, base=6))

The output of the following code will be

While converting from string to int you may get ValueError exception. This exception occurs if the string you want to convert does not represent any numbers. Suppose, you want to convert a hexadecimal number to an integer. But you did not pass argument base=16 in the int() function. It will raise a ValueError exception if there is any digit that does not belong to the decimal number system. The following example will illustrate this exception while converting a string to int.

"""
    Scenario 1: The interpreter will not raise any exception but you get wrong data
"""
num = '12'  # this is a hexadecimal value

# the variable is considered as decimal value during conversion
print('The value is :', int(num))

# the variable is considered as hexadecimal value during conversion
print('Actual value is :', int(num, base=16))

"""
    Scenario 2: The interpreter will raise ValueError exception
"""

num = '1e'  # this is a hexadecimal value

# the variable is considered as hexadecimal value during conversion
print('Actual value of \'1e\' is :', int(num, base=16))

# the variable is considered as decimal value during conversion
print('The value is :', int(num))  # this will raise exception

The output of the above code will be:

The value is : 12
Actual value is : 18
Actual value of '1e' is : 30
Traceback (most recent call last):
  File "/home/imtiaz/Desktop/str2int_exception.py", line 22, in 
    print('The value is :', int(num))  # this will raise exception
ValueError: invalid literal for int() with base 10: '1e'

Converting an int to string requires no effort or checking. You just use str() function to do the conversion. See the following example.

hexadecimalValue = 0x1eff

print('Type of hexadecimalValue :', type(hexadecimalValue))

hexadecimalValue = str(hexadecimalValue)

print('Type of hexadecimalValue now :', type(hexadecimalValue))

The output of the following code will be:

Type of hexadecimalValue : <class 'int'>
Type of hexadecimalValue now : <class 'str'>

That’s all about Python convert String to int and int to string conversion. Reference: Python Official Doc