Day 2 – Lesson 8 Fruitful Functions

1. Day 2 – Lesson 8Fruitful Functions Python Mini-Course University of Oklahoma Department of Psychology Python Mini-Course: Day 2 - Lesson 8

2. Lesson objectives • Understand how to return values from functions in Python • Create “fruitful” functions Python Mini-Course: Day 2 - Lesson 8

3. The power function revisited def power(base, exponent): val = base for x in range(1,exponent): val = val * base return val power(3,4) Python Mini-Course: Day 2 - Lesson 8

4. The return statement • Syntax return [expression] • Exists the enclosing function and returns the value of expression as a result of the call to the function • If expression is omitted, returns None Python Mini-Course: Day 2 - Lesson 8

5. The return statement • You can only return one value • That value can be any Python data type (including both built-in and custom data structures) • You can also use the return statement to exit a function early Python Mini-Course: Day 2 - Lesson 8

6. Exercise • Create a function that computes the distance between any two points when given their coordinates (in 2-D space) Python Mini-Course: Day 2 - Lesson 8

7. Distance function def distance(x1, y1, x2, y2): """Return the distance between points (x1, y1) and (x2, y2) as a float""" return 0.0 Python Mini-Course: Day 2 - Lesson 8

8. Distance function def distance(x1, y1, x2, y2): """Return the distance between points (x1, y1) and (x2, y2) as a float""" dx = x2 - x1 dy = y2 - y1 print 'dx is ', dx print 'dy is ', dy return 0.0 Python Mini-Course: Day 2 - Lesson 8

9. Distance function def distance(x1, y1, x2, y2): """Return the distance between points (x1, y1) and (x2, y2) as a float""" dx, dy = x2 - x1, y2 - y1 result = math.sqrt(dx**2 + dy**2) return result Python Mini-Course: Day 2 - Lesson 8

10. Distance function def distance(x1, y1, x2, y2): """Return the distance between points (x1, y1) and (x2, y2) as a float""" result = \ math.sqrt((x2-x1)**2 + (y2-y1)**2) return result Python Mini-Course: Day 2 - Lesson 8

11. Distance function def distance(x1, y1, x2, y2): """Return the distance between points (x1, y1) and (x2, y2) as a float""" return math.sqrt((x2-x1)**2 + (y2-y1)**2) Python Mini-Course: Day 2 - Lesson 8

12. Creating Boolean functions • Functions that return a Boolean value (True or False) can be used in conditional statements (i.e. if…else…) Python Mini-Course: Day 2 - Lesson 8

13. is_divisible function def is_divisible(x, y): if x % y == 0: return True else: return False is_divisible(16,4) is_divisible(16,3) Python Mini-Course: Day 2 - Lesson 8

14. is_divisible function def is_divisible(x, y): return x % y == 0 is_divisible(16,4) is_divisible(16,3) x, y = 16, 5 if is_divisible(x, y): print x,'is divisible by',y Python Mini-Course: Day 2 - Lesson 8

15. Next session • Iteration methods: • Recursion • Loops and conditional execution • The for loop • The while loop • Handling strings and text Python Mini-Course: Day 2 - Lesson 8

16. Suggested exercises • Exercise 5.1 – Fermat's Last Theorem • Exercise 6.6 – Palindromes • Exercise 6.7 – is_power function • Turtle exercises from Chaps 4 & 5 Python Mini-Course: Day 2 - Lesson 8