Converting a String to a Boolean in Python

In this article, we will discuss how to use the below functions to convert a string to a boolean in Python.

Using the Bool function:

The bool() function takes an argument and returns a boolean value based on the argument passed. If the argument is empty or evaluates to False, the function returns False. Otherwise, it returns True. Let's see some examples to understand how the bool() function works.

>>> bool('')
False
>>> bool('0')
True
>>> bool('1')
True
>>> bool('False')
True
>>> bool('True')
True

As you can see from the examples above, the bool() function returns False only when the argument is empty or evaluates to False. Otherwise, it returns True.

Now that we have understood how the bool() function works, let's see how to use it to convert a string to a boolean in Python.

s = 'True'
b = bool(s)
print(b)

In the example above, we have assigned a string 'True' to the variable s. We then pass this variable as an argument to the bool() function and assign the returned boolean value to the variable b. Finally, we print the value of b, which will be True.

Let's see another example:

s = 'False'
b = bool(s)
print(b)

In this example, we have assigned a string 'False' to the variable s. We then pass this variable as an argument to the bool() function and assign the returned boolean value to the variable b. Finally, we print the value of b, which will be True.

Wait, why did the bool() function return True even though the string 'False' was passed as an argument? This is because any non-empty string (except for '0') will evaluate to True when passed to the bool() function. Therefore, the string 'False' evaluates to True.

Using If Else Statement

So how do we handle cases where we want to convert a string to a boolean based on its actual value? One way to do this is to use an if statement to check the value of the string and assign the boolean value accordingly.

s = 'True'
if s == 'True':
    b = True
else:
    b = False
print(b)

In the example above, we have used an if statement to check if the value of the string s is 'True'. If it is, we assign True to the variable b. Otherwise, we assign False. Finally, we print the value of b, which will be True.

We can modify the above example to handle the string 'False' as well:

s = 'False'
if s == 'True':
    b = True
else:
    b = False
print(b)

In this example, we have checked if the value of the string s is 'True'. Since it is not, we assign False to the variable b. Finally, we print the value of b, which will be False.

While the above method works, it is not very efficient when dealing with multiple strings that need to be converted to booleans. In such cases, we can use a dictionary to map the string values to their boolean equivalents.

s = 'True'
d = {'True': True,'False': False}
b = d.get(s)
print(b)

In the example above, we have created a dictionary 'd' that maps the string values 'True' and 'False' to their boolean equivalents. We then use the `get()` method of the dictionary to retrieve the boolean value corresponding to the string value `s`. Finally, we assign the retrieved boolean value to the variable `b` and print its value.

Using dictionary:

Using a dictionary to map string values to boolean values is a more efficient way of converting multiple strings to booleans. It also makes the code easier to read and maintain.

There is another way to convert a string to a boolean in Python, which is by using the 'ast' (Abstract Syntax Trees) module. The 'ast.literal_eval()' function can be used to safely evaluate strings containing Python expressions, including boolean literals.

import ast

s = 'True'
b = ast.literal_eval(s)
print(b)

In the example above, we have imported the 'ast' module and used the 'literal_eval()' function to safely evaluate the string 's'. The function returns the boolean value corresponding to the string `s`, which we assign to the variable `b`. Finally, we print the value of `b`.

The 'ast.literal_eval()' function is useful when you want to evaluate strings that contain Python expressions other than boolean literals as well.