1. This Week The string type Modules print statement Writing programs if statements (time permitting) The boolean type (time permitting)

2. Review of Functions def Is a keyword parameters zero or more, comma-separated body One or more statements A return statement only exists in a function body Example def square(x): return x**2 def function_name(parameters): body

3. The Type String Single ‘…’ and double “…” quotes: ‘This is a string’ and “this is a string.” Triple ```…’’’ quote: ```This is a really long string that spans more than one line.’’’ Concatenation “Good ” + “Morning”  “Good Morning”

4. The print Statement When we want to output information to the screen we use print(). >>>print(“hello”) hello >>>print(“5+6=”, 5+6) 5+6=11 4

5. Writing Programs A file is a program when we make function calls inside the file. Q. How? Put the function call inside a “main clause” at the end of the file: if __name__ == '__main__': cube_volume(5)

6. Modules Sometimes we want to use some functions frequently Save them to a file, e.g., filename.py Include them with the Python command import filename We call this file a module.

7. Modules Python has builtin functions, e.g., –pow(x,y) returns x y –sqrt(x) returns √x Organized into different modules (stored in different files) pow(x,y) and sqrt(x) belong to the math module

8. More on import import math –Need to say math.pow(2,3) to use pow(,) –Prevents ambiguity –But inconvenient to type math.pow Solution –Only import specific functions: >>>from math import pow, sqrt –Import all functions when you know there are no conflicts >>>from math import * –Now we can say pow(2,3)

9. The __builtins__ Module Ways to get help with functions: –dir(module): list the functions in a module –help(function): show the docstrings for a function or module –import module: include the functions defined in a module

10. Documentation Strings Documentation Strings (docstrings) Use to explain the code Must be a string and the first line in a function or module Use complete, grammatically correct sentences Use parameter names, mention their types and describe the return value and type

11. The “if” Statement English example: Check The Temperature: If the temperature > 0 then it is “above the freezing point” Otherwise, if the temperature = 0 then it is “at the freezing point” Otherwise it is “below the freezing point”

12. The “if” Statement Python example: def check_temp(temperature): If the temperature > 0 then it is “above the freezing point” Otherwise, if the temperature = 0 then it is “at the freezing point” Otherwise it is “below the freezing point”

13. The “if” Statement Python example: def check_temp(temperature): if temperature > 0: return “above the freezing point” Otherwise, if the temperature = 0 then it is “at the freezing point” Otherwise it is “below the freezing point”

14. The “if” Statement Python example: def check_temp(temperature): if temperature > 0: return “above the freezing point” elif temperature == 0: return “at the freezing point” Otherwise it is “below the freezing point”

15. The “if” Statement Python example: def check_temp(temperature): if temperature > 0: return “above the freezing point” elif temperature == 0: return “at the freezing point” else: return “below the freezing point”

16. The “if” Statement EnglishPython If conditionif condition: Otherwise, if conditionelif condition: Otherwiseelse:

17. Nested “if” Statements English example: Check The Temperature: If the temperature > 0 then if the temperature >100 then it is “above the boiling point” Otherwise, if the temperature> 37 then it is “above body temperature” Otherwise, it is “above the freezing point” Otherwise, if the temperature = 0 then it is “at the freezing point” Otherwise it is “below the freezing point”

18. Nested “if” Statements English example: def check_temp(temperature): if temperature > 0: if the temperature >100 then it is “above the boiling point” Otherwise, if the temperature> 37 then it is “above body temperature” Otherwise, it is “above the freezing point” elif temperature == 0: return “at the freezing point” else: return “below the freezing point”

19. Nested “if” Statements English example: def check_temp(temperature): if temperature > 0: if temperature > 100: return “above the boiling point” Otherwise, if the temperature > 37 then it is “above body temperature” Otherwise, it is “above the freezing point” elif temperature == 0: return “at the freezing point” else: return “below the freezing point”

20. Nested “if” Statements English example: def check_temp(temperature): if temperature > 0: if temperature > 100: return “above the boiling point” elif temperature > 37: return “above body temperature” Otherwise, it is “above the freezing point” elif temperature == 0: return “at the freezing point” else: return “below the freezing point”

21. English example: def check_temp(temperature): if temperature > 0: if temperature > 100: return “above the boiling point” elif temperature > 37: return “above body temperature” else: return “above the freezing point” elif temperature == 0: return “at the freezing point” else: return “below the freezing point” Nested “if” Statements >100 >37 and <100 >0 and <37

22. Boolean These objects are either true or false. In Python, the type is bool. Examples >>> 3>5 >>> False >>> 2<10 >>> True

23. Combining Booleans: and, or, not true and true 3 2? True true and false 3 5? False false and false 6 5? False true or false 6 5? True not true not 1<4 False not false not 6<2 True

24. Relational Operators, =, ==, != Precedence: How does Python evaluate 25 < 12 + 35 ? 25 < 47 ? True Order: arithmetic  relational  boolean