Why Does \'1\' in \'11” == True Evaluate to False in Python?

Operator Precedence Conundrum in Python: Unraveling the Mystery of 'in' and Comparisons

The perplexing behavior observed with Python's 'in' operator and comparisons has left many bewildered. But beneath the surface lies a subtle interplay of operator precedence and expression chaining.

Operator precedence determines the order in which operations are evaluated within an expression. In Python, 'in' and comparison operators (e.g., '==') have equal precedence. Consequently, they are processed from left to right.

However, the situation becomes more intricate when chained expressions are involved. A common pitfall arises when attempting to compare the result of an 'in' operation with another value. Consider the following example:

<code class="python">'1' in '11' == True</code>

Surprisingly, this expression evaluates to False. The reason lies in the chaining of 'in' and '=='. The expression is effectively parsed as:

<code class="python">('1' in '11') and ('11' == True)</code>

The 'in' operator verifies whether '1' is a member of '11', resulting in True. However, the second comparison, '11' == True, yields False. Thus, the overall expression evaluates to False.

To obtain the desired True value, one must explicitly change the order of precedence. This can be achieved using parentheses:

<code class="python">('1' in '11') == True</code>

By enclosing the 'in' operation in parentheses, the expression is evaluated within its scope before comparing it with True. This alteration results in a True outcome as intended.

Understanding operator precedence and chaining is crucial in deciphering the behavior of complex Python expressions. It empowers developers to anticipate the sequence of operations and avoid unexpected pitfalls.

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