Python

• Exceptions
• Threading for compute bound tasks is synchronous
  • Python has a Global Interpreter Lock (GIL); mutex

Data

• Variable: symbolic name associated with location that contains a value or pointer
• Value: piece of data with a type that is either referred to by a variable or computed by a program expression
• Variable facets:
  • Name
  • Type
  • Value
  • Binding
  • Storage
  • Lifetime
  • Scope
  • Mutability
• Type: category of data
  • size/encoding, etc.
• Not every typed language must have typed variables
• Value vs reference types
• Strong typing: the language’s type system guarantees that all operations are only invoked on objects/values of appropriate types
• Weak typing: “” does not “”
• Static typing: prior to execution, type checker determines the type of every expression and ensures all operations are compatible with the types of their operands
• Dynamic typing: as the program executes, the type checker ensures that each primitive operation is invoked with values of the right types, and raises an exception otherwise