Why Isn\'t My \"Not In\" Check for Tuples Working in Python?

Verifying Presence of Elements in a Python List

When working with lists in Python, it's often necessary to check if a specific element is present or absent. For conditional branches that rely on the absence of an element in a list, the following syntax is commonly used:

<code class="python">if element not in list:
    # Code to execute if element is not in the list</code>

However, a user has encountered an issue where this syntax is not functioning as expected for a list of tuples.

The Issue

The provided code attempts to check if a tuple is not in a list and proceed with a specific action only if the tuple is absent:

<code class="python">if curr_x -1 > 0 and (curr_x-1 , curr_y) not in myList:

    # Do Something</code>

The user notes that this code fails to execute the intended action under certain circumstances.

The Solution

The provided syntax for checking if an element is not in a list is correct and should work without issue. Therefore, the error likely lies elsewhere in the code.

To troubleshoot this problem, the following steps can be taken:

1. Review the values of curr_x, curr_y, and myList during the conditional check: Ensure that the tuple (curr_x-1, curr_y) is not present in myList when the conditional is evaluated as False.
2. Check the indentation of the conditional code block: Verify that the intended action is properly indented within the if block.
3. Debug the code by printing intermediate values: Use print statements or a debugger to display the values of curr_x, curr_y, myList, and the result of the conditional check at runtime. This will help isolate the cause of the issue.

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