Erle Robotics Learning Python GitBook Free

Exercises: Functions

Exercise 1

Write a shutting down program:

First, def a function, shut_down, that takes one argument s. Then, if the shut_down function receives an s equal to "yes", it should return "Shutting down" Alternatively, elif s is equal to "no", then the function should return "Shutdown aborted". Finally, if shut_down gets anything other than those inputs, the function should return "Sorry".

Exercise 2

Import the math module in whatever way you prefer. Call its sqrt function on the number 13689 and print that value to the console.

Exercise 3

First, def a function called distance_from_zero, with one argument (choose any argument name you like). If the type of the argument is either int or float, the function should return the absolute value of the function input. Otherwise, the function should return "Nope". Check if it works calling the function with -5.6 and "what?".

Exercise 4

Rewrite your pay computation program (previus chapter) with time-and-a-half for overtime and create a function called computepay which takes two parameters (hours and rate).

Enter Hours: 45
Enter Rate: 10
Pay: 475.0

Exercise 5

Let's use functions to calculate your trip's costs:

• Define a function called hotel_cost with one argument nights as input. The hotel costs $140 per night. So, the function hotel_cost should return 140 * nights.
• Define a function called plane_ride_cost that takes a string, city, as input. The function should return a different price depending on the location, similar to the code example above. Below are the valid destinations and their corresponding round-trip prices.

  "Charlotte": 183
  "Tampa": 220
  "Pittsburgh": 222
  "Los Angeles": 475
  

  -Below your existing code, define a function called rental_car_cost with an argument called days. Calculate the cost of renting the car: Every day you rent the car costs $40.(cost=40*days) if you rent the car for 7 or more days, you get $50 off your total(cost-=50). Alternatively (elif), if you rent the car for 3 or more days, you get $20 off your total. You cannot get both of the above discounts. Return that cost. -Then, define a function called trip_cost that takes two arguments, city and days. Like the example above, have your function return the sum of calling the rental_car_cost(days), hotel_cost(days), and plane_ride_cost(city) functions.
• Modify your trip_cost function definion. Add a third argument, spending_money. Modify what the trip_cost function does. Add the variable `spending_money to the sum that it returns.

Exercise 6

Follow the stpes:

• First, def a function called cube that takes an argument called number.
• Make that function return the cube of that number (i.e. that number multiplied by itself and multiplied by itself once again).
• Define a second function called by_three that takes an argument called number. if that number is divisible by 3,by_threeshould call cube(number) and return its result. Otherwise, by_three should return False. -Check if it works.

Solutions

Exercise 1

>>> def shut_down(s):
...     if s=="yes":
...        return "Shutting down"
...     elif s=="no":
...        return "Shutdown aborted"
...     else:
...        return "Sorry"
...
>>> s="no"
>>> shut_down(s)
'Shutdown aborted'
>>>

Exercise 2

>>> from math import sqrt
>>> print sqrt(13689)
117.0

Exercise 3

>>> def distance_from_zero(num):
...     if type(num)== int or type(num)== float:
...         return abs(num)
...     else:
...         return "Nope"
...
>>> distance_from_zero(-5.6)
5.6
>>> distance_from_zero("what?")
'Nope'

Exercise 4

>>> def computepay(hours,rate):
...     if hours < 40:
...        pay=hours*rate
...        print "the pay is:", pay
...     else:
...        pay = 40 * rate + (hours-40)*1.5*rate
...        print "the pay is:", pay
...
>>>
>>> hours=raw_input("Enter worked hours:")
Enter worked hours:45
>>> hours=float(hours)
>>> rate=10
>>> computepay(hours,rate)
the pay is: 475.0
>>>

Exercise 5

Store this in a file. You can use vi text editorand open a .py file, save and execute it:

root@erlerobot:~# vi trpcal.txt
root@erlerobot:~# cp trpcal.txt trpcal.py
root@erlerobot:~# python trpcal.py

This is the code:

nights=raw_input("Enter nights:")
city=raw_input("Enter city:")
days=raw_input("Enter days of car rental:")
spending_money=raw_input("Enter money:")

def hotel_cost(nights):
    return 140*nights

def plane_ride_cost(city):
    if city=="Charlotte":
        return 183
    elif city=="Tampa":
        return 220
    elif city=="Pittsburgh":
        return 222
    elif city=="Los Angeles":
        return 475


def rental_car_cost(days):
    cost=days*40
    if days >= 7:
        cost -= 50
    elif days>=3:
        cost-=20
    return cost

def trip_cost(city,days,spending_money):
    print rental_car_cost(days)+hotel_cost(days)+plane_ride_cost(city)+spending_money

trip_cost(city,days,spending_money)

Exercise 6

>>> def cube(number):
...     return number*number*number
...
>>> def by_three(number):
...    if number %3 ==0:
...       return cube(number)
...    else:
...       return False
...
>>> by_three(9)
729
>>>