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literal-comparison.md

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Pattern: Comparison to literal

Issue: -

Description

Used when comparing an object to a literal, which is usually what you do not want to do, since you can end up comparing to a different literal than what was expected altogether. Also note that is is for identity testing, == is for equality testing.

Example of incorrect code:

test_string = "ok"
if test_string is "ok": # Returns true
    # do stuff

Both strings are actually stored in the same memory location, they have the same identity, so the is operator works as expected. But if you construct a string by some other method (even if that string contains exactly the same characters), then the string may be equal, but it is not the same string - that is, it has a different identity, because it is stored in a different place in memory.

Example of correct code:

test_string = "ok"
if test_string == "ok":
    # do stuff

Further Reading