What are signals in Django and how are they used?
Instruction: Define Django signals and provide examples of their usage.
Context: This question assesses the candidate's understanding of signals in Django, a framework feature for allowing decoupled applications to receive notifications when certain actions occur.
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Signals notify registered receivers when an event occurs. Django provides model and request signals, and an application can define its own. They can connect independent components, but also hide control flow; an explicit service call is often clearer when both sides belong to the same business operation.
This complete Django5.2 example demonstrates synchronous dispatch and its returned receiver result without sending email or writing to a database:...