Why is my Tuple Check in a Python List Not Working?

Checking Tuple Presence in a Python List

In Python, you can efficiently determine if a tuple exists within a list using the "not in" operator. However, a user reported an issue where their conditional statement involving tuple presence was not functioning correctly.

The user's code attempted to execute a specific action only if a tuple was not present in a list called "myList":

if curr_x -1 > 0 and (curr_x-1 , curr_y) not in myList:

# Do Something

However, this condition was not being met as expected.

Troubleshooting the Code

The provided code appears correct in principle. The "not in" operator should effectively evaluate whether the specified tuple is absent from the list. To isolate the issue, it is recommended to double-check the following aspects:

• Verify that "curr_x -1 > 0" is evaluating to True when intended.
• Ensure that "myList" is a valid list object.
• Check that (curr_x-1, curr_y) is a tuple of the correct elements and type.
• Examine the code preceding and following the conditional statement to identify any potential bugs.

Example Usage

To demonstrate the correct usage of the "not in" operator for tuple presence checking, consider the following examples:

3 not in [2, 3, 4]
False
3 not in [4, 5, 6]
True

Or with tuples:

(2, 3) not in [(2, 3), (5, 6), (9, 1)]
False
(2, 3) not in [(2, 7), (7, 3), "hi"]
True

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