Explain is vs == in Python.

Summary

== checks value equality, while is checks whether two variables reference the exact same object.

Longer Answer

Classes can customize == through eq, so two different objects can compare equal. The is operator cannot be customized; it compares object identity, which is why it is appropriate for sentinels such as None, NotImplemented, and custom singleton markers.

Do not use is for strings, integers, or other values just because it appears to work in a REPL. Interning and caching are implementation details and can make identity checks pass accidentally.

Key Points

• Classes can customize == through eq, so two different objects can compare equal
• The is operator cannot be customized; it compares object identity, which is why it is appropriate for sentinels such as None, NotImplemented, and custom singleton markers
• Do not use is for strings, integers, or other values just because it appears to work in a REPL
• For 'Explain is vs == in Python.', a strong interview answer should define the mechanism, name the common failure mode, and explain the production decision it affects.

Do not use is for strings, integers, or other values just because it appears to work in a REPL. Interning and caching are implementation details and can make identity checks pass accidentally

Comparison / Tradeoffs

Summary

== checks value equality, while is checks whether two variables reference the exact same object.

Longer Answer

For 'Explain is vs == in Python.', a strong interview answer should define the mechanism, name the common failure mode, and explain the production decision it affects.

Do not use is for strings, integers, or other values just because it appears to work in a REPL. Interning and caching are implementation details and can make identity checks pass accidentally.

Key Points

• For 'Explain is vs == in Python.', a strong interview answer should define the mechanism, name the common failure mode, and explain the production decision it affects
• Do not use is for strings, integers, or other values just because it appears to work in a REPL
• Interning and caching are implementation details and can make identity checks pass accidentally
• Use the answer to connect the concept back to a realistic production or interview scenario for 'Explain is vs == in Python.'

Comparison / Tradeoffs