Why Does `bool(\'False\')` Return `True` in Python?

Converting String to Boolean in Python

Converting a string to a boolean in Python seems straightforward, but it can lead to unexpected results. Consider the following example:

<code class="python">>>> bool("False")
True</code>

Why does this code return True instead of False?

The key to understanding this behavior lies in Python's implicit casting. When converting a string to a boolean, Python evaluates the string's content. If the string is empty, it's considered False, otherwise it's considered True.

Solution:

To correctly convert a string to a boolean based on its expected value, it is recommended to compare the string to the expected boolean representation. For example:

<code class="python">s == 'True'</code>

This approach explicitly checks if the string matches the expected boolean value.

For more flexibility in parsing, you can check against a list of accepted true values:

<code class="python">s.lower() in ['true', '1', 't', 'y', 'yes', 'yeah', 'yup', 'certainly', 'uh-huh']</code>

Caution:

Using the following conversion can lead to unexpected outcomes:

<code class="python">bool("foo")
True
bool("")
False</code>

Empty strings evaluate to False, but all other strings evaluate to True. This behavior is not suitable for parsing purposes.

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