Function Examples
Announcements
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Describing Functions
Boolean Favorites def likes(n): """Returns whether George Boole likes the non-negative integer n.""" ... def mystery1(n): likes = is_prime One approach: n = 8 k = 1 1. Read the code while k < n: 2. Read the description options if likes(n): 3. Consider an example print(k) k = k + 2 all odd numbers but only if George likes n mystery1 prints ______ less than n ______ . mystery1 prints all odd numbers less than n that George likes. 6
Boolean Favorites def likes(n): """Returns whether George Boole likes the non-negative integer n.""" ... def mystery2(n): One approach: i, j, k = 0, None, None 1. Read the code while i < n: 2. Read the description options if likes(i): 3. Consider an example if j != None and (k == None or i - j < k): k = i - j j = i i = i + 1 return k the smallest difference between There are no two two positive integers below n such integers that George likes mystery 2 returns ______ or returns None if ______ . 7
Generating Environment Diagram
A Day at the Beach def flip(flop): not true for flop == 1 flop>2 if ______: true for flop == 3 return None ______ lambda flip: 3 flip = ______ return flip def flop(flip): return flop flip, flop = flop, flip ______ flip(____)(3) flop(1)(2) 9
Implementing Functions
Implementing a Function def remove(n, digit): Read the description """Return all digits of non-negative N that are not DIGIT, for some 231 4 3 Verify the examples & pick a simple one non-negative DIGIT less than 10. 1 1 >>> remove(231, 3) Read the template 21 + 20 + 30 >>> remove(243132, 2) Implement without the template, then change 4313 + 200 your implementation to match the template. """ OR 21 231 kept, digits = 0, 0 If the template is helpful, use it. n > 0 while ________________________________: Annotate names with values from your chosen example n, last = n // 10, n % 10 last != digit Write code to compute the result if _______________________________: **digits 10* kept + last *10 Did you really return the right thing? kept = _______________________ digits + 1 231 21 digits = _____________________ Check your solution with the other examples kept return _______________________________ 11
Implementing a Function def remove(n, digit): Read the description """Return all digits of non-negative N that are not DIGIT, for some 231 3 Verify the examples & pick a simple one non-negative DIGIT less than 10. >>> remove(231, 3) Read the template 21 >>> remove(243132, 2) Implement without the template, then change 4313 your implementation to match the template. """ OR kept, digits = 0, 0 If the template is helpful, use it. n > 0 while ________________________________: Annotate names with values from your chosen example n, last = n // 10, n % 10 last != digit Write code to compute the result if _______________________________: kept + last /10 Did you really return the right thing? kept = _______________________ digits + 1 21 digits = _____________________ Check your solution with the other examples round( kept * 10 ** (digits-1) ) return _______________________________ 12
Decorators
Function Decorators (Demo) Function decorator @trace1 Decorated def triple(x): function return 3 * x is identical to Why not just def triple(x): use this? return 3 * x triple = trace1(triple) 14
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