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#!/usr/bin/python -tt

# Copyright 2010 Google Inc.

# Licensed under the Apache License, Version 2.0

# http://www.apache.org/licenses/LICENSE-2.0

# Google's Python Class

# http://code.google.com/edu/languages/google-python-class/

# Basic string exercises

# Fill in the code for the functions below. main() is already set up

# to call the functions with a few different inputs,

# printing 'OK' when each function is correct.

# The starter code for each function includes a 'return'

# which is just a placeholder for your code.

# It's ok if you do not complete all the functions, and there

# are some additional functions to try in string2.py.

# A. donuts

# Given an int count of a number of donuts, return a string

# of the form 'Number of donuts: <count>', where <count> is the number

# passed in. However, if the count is 10 or more, then use the word 'many'

# instead of the actual count.

# So donuts(5) returns 'Number of donuts: 5'

# and donuts(23) returns 'Number of donuts: many'

def donuts(count):

if count > 9:

amt = 'many'

else:

amt = str(count)

return 'Number of donuts: ' + amt

# B. both_ends

# Given a string s, return a string made of the first 2

# and the last 2 chars of the original string,

# so 'spring' yields 'spng'. However, if the string length

# is less than 2, return instead the empty string.

def both_ends(s):

if len(s) < 2:

return ''

return s[0:2] + s[-2:]

# C. fix_start

# Given a string s, return a string

# where all occurences of its first char have

# been changed to '*', except do not change

# the first char itself.

# e.g. 'babble' yields 'ba**le'

# Assume that the string is length 1 or more.

# Hint: s.replace(stra, strb) returns a version of string s

# where all instances of stra have been replaced by strb.

def fix_start(s):

char = s[0]

length = len(s)

s = s.replace(char, '*')

s = char + s[1:]

return s

# D. MixUp

# Given strings a and b, return a single string with a and b separated

# by a space '<a> <b>', except swap the first 2 chars of each string.

# e.g.

# 'mix', pod' -> 'pox mid'

# 'dog', 'dinner' -> 'dig donner'

# Assume a and b are length 2 or more.

def mix_up(a, b):

new_a = b[:2] + a[2:]

new_b = a[:2] + b[2:]

return new_a + ' ' + new_b

# Provided simple test() function used in main() to print

# what each function returns vs. what it's supposed to return.

def test(got, expected):

if got == expected:

prefix = ' OK '

else:

prefix = ' X '

print '%s got: %s expected: %s' % (prefix, repr(got), repr(expected))

# Provided main() calls the above functions with interesting inputs,

# using test() to check if each result is correct or not.

def main():

print 'donuts'

# Each line calls donuts, compares its result to the expected for that call.

test(donuts(4), 'Number of donuts: 4')

test(donuts(9), 'Number of donuts: 9')

test(donuts(10), 'Number of donuts: many')

test(donuts(99), 'Number of donuts: many')

print

print 'both_ends'

test(both_ends('spring'), 'spng')

test(both_ends('Hello'), 'Helo')

test(both_ends('a'), '')

test(both_ends('xyz'), 'xyyz')

print

print 'fix_start'

test(fix_start('babble'), 'ba**le')

test(fix_start('aardvark'), 'a*rdv*rk')

test(fix_start('google'), 'goo*le')

test(fix_start('donut'), 'donut')

print

print 'mix_up'

test(mix_up('mix', 'pod'), 'pox mid')

test(mix_up('dog', 'dinner'), 'dig donner')

test(mix_up('gnash', 'sport'), 'spash gnort')

test(mix_up('pezzy', 'firm'), 'fizzy perm')

# Standard boilerplate to call the main() function.

if __name__ == '__main__':

main()