string1.py

#!/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 < 10:
        return 'Number of donuts: ' + str(count)  
    return 'Number of donuts: many'
# or
def donuts_2(count):
    res = 'Number of donuts: '
    if count < 10:
        res += str(count)
    else:
        res += 'many'
    return res
# or
def donuts_3(count):
    return 'Number of donuts: {0}' .format(count if count <= 9 else 'many')


# 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[:2] + s[-2:]
    
# or

def both_ends2(s):
    return '' if len(s) <= 1 else s[:2] + s[-2:]

# or bether

def both_ends3(s):
    return s[:2] + s[-2:] if len(s) >= 2 else ''


# 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# where all instances of stra have been replaced by strb.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):
    head, tail = s[0],s[1:] 
    return head + tail.replace(head, '*')
    
 # or
def fix_start2(s):
    return s[0] + s[1:].replace(s[0], '*')


# 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):
    return b[:2] + a[2:] + ' ' + a[:2] + b[2:]
    
# or bether
def mix_up2(a, b):
    parts = [b[:2], a[2:], ' ', a[:2], b[2:]]
    return ''.join(parts)


# 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('donuts  2')
    # Each line calls donuts, compares its result to the expected for that call.
    test(donuts_2(4), 'Number of donuts: 4')
    test(donuts_2(9), 'Number of donuts: 9')
    test(donuts_2(10), 'Number of donuts: many')
    test(donuts_2(99), 'Number of donuts: many')
    
    print()
    print('donuts 3')
    # Each line calls donuts, compares its result to the expected for that call.
    test(donuts_3(4), 'Number of donuts: 4')
    test(donuts_3(9), 'Number of donuts: 9')
    test(donuts_3(10), 'Number of donuts: many')
    test(donuts_3(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('both_ends 2')
    test(both_ends2('spring'), 'spng')
    test(both_ends2('Hello'), 'Helo')
    test(both_ends2('a'), '')
    test(both_ends2('xyz'), 'xyyz')
    
    print()
    print('both_ends 3')
    test(both_ends3('spring'), 'spng')
    test(both_ends3('Hello'), 'Helo')
    test(both_ends3('a'), '')
    test(both_ends3('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('fix_start 2')
    test(fix_start2('babble'), 'ba**le')
    test(fix_start2('aardvark'), 'a*rdv*rk')
    test(fix_start2('google'), 'goo*le')
    test(fix_start2('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')
    
    print()
    print('mix_up 2')
    test(mix_up2('mix', 'pod'), 'pox mid')
    test(mix_up2('dog', 'dinner'), 'dig donner')
    test(mix_up2('gnash', 'sport'), 'spash gnort')
    test(mix_up2('pezzy', 'firm'), 'fizzy perm')


# Standard boilerplate to call the main() function.
if __name__ == '__main__':
    main()