程序代写代做代考 ISYS90088

ISYS90088
Introduction to Application

Development

Week 10 – Contd. from week 9 on functions

Semester 2 , 2018

Dr Antonette Mendoza

Recap: Functions and return statement

A value-returning function has a return statement that
returns a value back to the part of the program that called
it.

Syntax:
def ():
statement
statement
statement
return

Functions and return statement

•  The value of the expression that follows the key word
return will be sent back to part of the program that
called this function. This can be any value, expression,
or variable that has a value.

•  A return statement can also send back:
– Strings
– boolean values
– multiple values

(recap)Examples 1: return statement

# write a program that converts cenlius to farenheit

def C2F(n):
return 9*n/5 + 32

def main():
cels = int(input(‘enter a value in celcius:’))
f = C2F(cels)
print(f)

main()
4

(recap) Examples 2: return statement
def main():
# get the user’s age
first_age = int(input(‘enter your age:’))
# get the users best friends age
second_age = int(input(‘enter your best friends age:’))
# get the sum of both ages
total = sum (first_age, second_age)
# display the total age
print(‘their total age is:’, total, ‘years old’)

#sum function accepts two int arguments & returns sum of those
arguments
def sum(num1, num2):
result = num1 + num2
return result
#call main function
main()

Returning strings

def get_name():
name = input(‘enter your name:’)
return name

def main():
print(‘this example prints a name given by
user:’)
user_name = get_name()
print(‘my name is’ , user_name)

main()

Quiz!

•  What is printed to the screen here?

def bloodify1(word):
return word[:3] + ‘-bloody-‘ + word[3:]

print(bloodify1(‘fantastic’))

Returning boolean values

•  You receive an integer from the user. Write a function
that checks whether or not this integer is even or odd
and returns a boolean.

Ø What are the tasks in this program?
– accept value from user (main function)

– checks whether the value is even (funct to check)

or odd and returns a boolean

– print back a response (main function)

– and don’t forget to call the main!!!

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return for boolean values
p9
example:

def main():
number = int(input(‘enter a number:’))
if is_even (number):
print(‘the number is even’)
else:
print(‘the number is odd’)

# how do you check if a number si even or odd
#number % 2 == 0 will help you do that

def is_even(num1):
if (num1 % 2) == 0:
status = True
else:
status = False
return status

main()

p10 return for multiple values

p11 return for multiple values: tuples

Example: Returning boolean values
* fill relevant statements in the place marked XXX

def main():
number = int(input(‘enter a number:’))
if XXX:
print(‘the number is even’)
else:
print(‘the number is odd’)

# how do you check if a number is even or odd

def is_even(num1):
if (XXX) == 0:
status = True
else:
status = False
return XXX

main()

Returning multiple values

Syntax:
return expr1, expr2, expr..etc…

Example:
#a function to accept first and last name and then print out your
full name

def get_name():
first = input(‘enter your first name:’)
last = input(‘enter your last name:’)
return first, last

def main():
first_name, last_name = get_name()
print(‘My name is:’, first_name, last_name)

main()

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returning for multiple values:

#alternative
def get_name():
first = input(‘enter your first name:’)
last = input(‘enter your last name:’)
return first, last

def main ():
name = get_name ()
print (“my name is”,name)

main()

output:
my name is (‘sarah’, ‘hong’) not as same as the original one
my name is: sarah hong

Returning multiple values: tuples
def checking_tuple(x):
sum = x + 1
mult = x * 3
exp = x ** 3
return (sum, mult, exp)

def main():
num = 5
(a, b, c) = checking_tuple(num)
print(a,b,c)
main()

Key arguments
•  While generally , arguments are passed by position to

parameter variables in functions, you can also specify
which parameter variable the argument should be
passed to.

Syntax:
parameter_name = value

In this format, parameter_name is the parameter and
value is the value being passed to that parameter.

An argument written in this format is called a key
argument.

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key argument: choose which parameter the argument should be passed to:

parameter_name = value
assign a specific value to parameter

p13 example:
3 arguments that pass to 3 specific parameters.

Key arguments: examples

def main():
show_interest(rate = 0.01, periods = 10,
principal = 100000.0)

def show_interest(principal, rate, periods):
interest = principal * rate * periods
print(‘The simple interest will be $%.2f’ %
interest)

main()

Mixing Key arguments with positional
arguments : examples

•  You can mix keyword arguments with positional arguments.
Positional arguments must come first followed by keyword
arguments

def main():
show_interest(10000.0, periods = 20, rate = 0.01)

def show_interest(principal, rate, periods):
interest = principal * rate * periods
print(‘The simple interest will be $%.2f’ %
interest)

main()

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key argument and positional argument 的结合：
rule: positional argument 必须在 key argument 的前面

Functions and Processing lists – passing lists
as arguments

•  Write a function that calculates the total of the values in a list:

#function to calculate the total in a list of numbers
def main():
#create a list
numbers = [1,2,3,4,5,6]
print(‘the total is’, get_total(numbers))

def get_total(list1):
# create an accumulator
total = 0
for num in list1:
total = total + num
return total

main()

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passing lists as aarguments:
目前为止，argument 可以是 lists，number，string，tuple，之后也会说到，可以是dictionary.

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in reality, 一般不会直接告诉你list是什么，会让你写一个程序自己组建list。

#alternative
def main():
numbers = get_values()
print(‘the number in the list are:’)
print (numbers)
def get_values():
values = []
again = ‘y’
while again == ‘y’:
num = int(input(‘enter a number:’))
values.append(num)
print (‘do you want to enter another number?’)
again = input(‘y=yes, anything else = no:’)
print () #空一行的意思
return values
main()

Functions and Processing lists – passing lists
as arguments

•  Write a function that calculates the average of the values in a list and
returns the average and the total:

def main():
#create a list
numbers = [1,2,3,4,5,6]
total = 0
print(‘the total is’, get_average(numbers, total))

def get_average(list1,t):
# create an accumulator
total = 0.0
for num in list1:
total = total + num
average = total/len(list1)
return average, total

main()

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passing lists as arguments
the parameter t doesn’t do any calculation but we still need it, as it need to match with arguments.

Functions & Processing lists – returning a list

•  A function can return a reference to a list.
•  For example, you might create a list, add items into it and then

return a reference to the list so that parts of the program can
work on it.

def main():
# get a list with values stored in it
numbers = get_values()
print(‘the numbers in the list are:’,
numbers)

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returning a list:
p17-p18

Functions & Processing lists – returning a list
def get_values():
#create an empty list
values = []
#create a variable to control the loop
again = ‘y’
# get values from the user and add into the list
while again == ‘y’:
num = int(input(‘enter a number:’))
values.append(num)
#to add more items in the list
print(‘do you want to enter another number?’)
again = input(‘y = yes, anything else = no:’)
print()
return values
main()

Functions and Processing lists – passing lists
as arguments – try this!

•  Write
a
program
that
uses
two
func8on
that
gets
a
series
of
test
scores

and
calculates
the
average
of
the
scores
with
the
lowest
score
dropped:

def main():
#create a list of scores
scores = get_values()
# calculates the total of the list of elements
total = get_total(scores)
lowest = min(scores)
#subtract the lowest from the list
total = total – lowest
average = total/(len(scores) – 1)
print(‘the average is, with the lowest dropped out:’,
average)

main()
# see example code for the functions get_values and
get_total

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def main():
# get a list with values stored in it
scores = get_values()
print(‘the numbers in the list are:’)
print(scores)
total = get_total(scores)
print(total)
# now for the dropping of the lowest score
lowest = min(scores)
#subtract the lowest from the list
total = total – lowest
#print(total)
average = total/(len(scores) – 1)
print(‘the average is, with the lowest dropped out:’, average)

def get_values():
#create an empty list
values = []
#create a variable to control the loop
again = ‘y’
# get values from the userand add into the list
while again == ‘y’:
num = int(input(‘enter a number:’))
values.append(num)

#to add more items in the list
print(‘do you want to enter another number?’)
again = input(‘y = yes, anything else = no:’)
print()
return values

def get_total(nums):
t=0
for n in nums:
t = t + n
return t

main()