REPL

1. REPL Read-Eval-Print-Loop (or Interactive Environment)

4. Recap What have we learned so far?

5. Program = Data + Operations + Assignment + Control Flow

6. Data • Primitive Type • int • float • string • boolean • Compound Type • list

7. Operations • Arithmetic • +, -, *, //, % etc. • Boolean • and, or, not • <, <=, >, >=, ==, != • String • +, *, [], [:], str(), len etc. • List • +, [], split, join

8. Expressions • Combinations of data and their operations • Arithmetic • Boolean • Have precedence and associativity rules to determine order of evaluation • When in doubt, use parentheses ()

9. Assignment and Variables • Variables • Places where data (or values) can be stored • Names at the high-level • Storages (or memory locations) at the low-level • Assignment • The act of placing data (or values) to names (or placeholders) • Variables on LHS = Expressions on RHS

10. Controlling Program Flow: If-Else if <boolean expression 1>: [code guarded by boolean expression 1] elif<boolean expression 2>: [code guarded by boolean expression 2] else: [code to execute if all fail (False)]

11. Controlling Program Flow: While while <boolean expression >: [while code block] [outside while code block]

12. Functions • A way of organizing code • Easy to reason about program flow • Modularity in software • Define a function and make a function call to it • A function definition by itself is an idle code until you activate it with a call to it

13. Example Function def fact(n): if n == 0: return 1 else: return fact(n-1)*n print fact(12) print fact(0) print fact(5)