HW2

1. Flip Sign and Add Three.

Write a short program (not a function definition) that will get a decimal value x (type float) from standard input and print a message regarding the value of x and the value of 3 - x.

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For example:

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Input	Result
5.5 🔗	x is 5.5 and 3 - x is -2.5 🔗
-8.1 🔗	x is -8.1 and 3 - x is 11.1 🔗
0.12 🔗	x is 0.12 and 3 - x is 2.88 🔗

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2. Calculate the Ratio as a Percentage.

Write the code needed to get two float values from standard input, A and B. Calculate A as a percentage of B, rounded to one decimal place. For example, if A is 25.0 and B is 75.0, A is about 33.3% of B since 25.0 / 75.0 = 1 / 3 = .3333333... (multiply the ratio by 100 to get the percentage).

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Print a message to report the result (using the same format as shown in the examples below).

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For example:

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Input	Result
5 15 🔗	5.0 is about 33.3 percent of 15.0 🔗
12.5 28.0 🔗	12.5 is about 44.6 percent of 28.0 🔗
2.52 8.1 🔗	2.52 is about 31.1 percent of 8.1 🔗

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3. Rounded Square Root.

Write the code needed to get an integer value from standard input, calculate the square root of the value rounded to the nearest hundredth, then print a message with the result.

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NOTE: You may assume that the input value will not be negative.

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Reminder:

Start by importing the math module.

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Use the function math.sqrt to calculate a square root.

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For example:

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Input	Result
11 🔗	the square root of 11 is about 3.32 🔗
95 🔗	the square root of 95 is about 9.75 🔗
3 🔗	the square root of 3 is about 1.73 🔗

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4. Round Float.

Write the code needed to get two numbers from standard input:

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a decimal value (i.e., a number with a decimal point, which will be read as Python type float)

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an integer value

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Assign the decimal value to the variable decimal and the integer value to the variable precision (or other reasonable names).Finally, round the value of decimal to the number of places after the decimal point indicated by precision, and print the result.

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For example:

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Input	Result
5.555 1 🔗	5.6 🔗
-9.87437 3 🔗	-9.874 🔗
0.900001 0 🔗	1.0 🔗
-42.4444 1 🔗	-42.4 🔗

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5. Integer Division and Remainder.

Write the code needed to get two integer values from standard input, assign the first integer to the variable dividend, and assign the second integer to the variable divisor. Calculate two things and print the results:

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Use integer division (floor division) to calculate how many times the divisor will go into the dividend, excluding the remainder.

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Use the remainder operator to calculate the integer remainder that will be left over when the dividend is divided by the divisor.

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For example:

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Input	Result
10 7 🔗	7 goes into 10 1 times with 3 left over 🔗
100 35 🔗	35 goes into 100 2 times with 30 left over 🔗
10 5 🔗	5 goes into 10 2 times with 0 left over 🔗

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6. Bookcases.

You are planning to add bookcases to a wall in your living room, but you don’t know how many bookcases to buy. You decide to write a Python function, get_num_bookcases, to help. Your function needs to do the following:

Take parameters for the width of the wall (an integer number of feet) and the width of a bookcase (an integer number of inches). (Your function does not read input from the keyboard; it gets its input through named parameters.)

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Calculate how many whole bookcases will fit on the wall using modular arithmetic (use div and/or mod, represented by the operators // and %, as needed to solve the problem).

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Returnthe number of bookcases.

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For example:

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Test	Result
print(get_num_bookcases(20, 50)) 🔗	4 🔗
print(get_num_bookcases(8, 15)) 🔗	6 🔗
print(get_num_bookcases(3, 40)) 🔗	0 🔗

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7. Detect Even/Odd.

Write a function with no parameters, even_or_odd()

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Specifications:

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read an integer from standard input

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return 0 if the integer is even, 1 if the integer is odd

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do not use a conditional ("if") statement, just use modular arithmetic (such as // or %)

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do not print the result, return it

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Hint: What is the remainder when you divide an even number by 2? What is the remainder when you divide an odd number by 2?

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For example:

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Test	Input	Result
ans = even_or_odd() print(ans) 🔗	5 🔗	1 🔗
ans = even_or_odd() print(ans) 🔗	-14 🔗	0 🔗
ans = even_or_odd() print(ans) 🔗	0 🔗	0 🔗
ans = even_or_odd() print(ans) 🔗	99 🔗	1 🔗

import sys
def input(prompt=None):
  if prompt is not None:
    print(prompt, end='')
  line = sys.stdin.readline()
  if len(line) > 0 and line[-1] == "\n":
    return line[:-1]
  return line

^^^^
====
from unittest.gui import TestCaseGui
import StringIO
import sys

class myTests(TestCaseGui):

def test1(self):
    sys.stdin = StringIO.StringIO("5")
    res = even_or_odd()
    sys.stdin = sys.__stdin__
    self.assertEqual(res, 1, "Input: 5")

def test2(self):
    sys.stdin = StringIO.StringIO("-14")
    res = even_or_odd()
    sys.stdin = sys.__stdin__
    self.assertEqual(res, 0, "Input: -14")

def test3(self):
    sys.stdin = StringIO.StringIO("0")
    res = even_or_odd()
    sys.stdin = sys.__stdin__
    self.assertEqual(res, 0, "Input: 0")

def test4(self):
    sys.stdin = StringIO.StringIO("99")
    res = even_or_odd()
    sys.stdin = sys.__stdin__
    self.assertEqual(res, 1, "Input: 99")

def test5(self):
    sys.stdin = StringIO.StringIO("50")
    res = even_or_odd()
    sys.stdin = sys.__stdin__
    self.assertEqual(res, 0, "Input: 50")

def test6(self):
    sys.stdin = StringIO.StringIO("-121")
    res = even_or_odd()
    sys.stdin = sys.__stdin__
    self.assertEqual(res, 1, "Input: -121")

def test7(self):
    sys.stdin = StringIO.StringIO("122")
    res = even_or_odd()
    sys.stdin = sys.__stdin__
    self.assertEqual(res, 0, "Input: 122")

myTests().main()

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8. Spam, N Times.

Write a function, say_spam(⁠⁠n); it takes an integer parameter n and prints "Spam!" n times in response.

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You should assume n > 0 for this function.

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Hint: Use a simple for loop with a print statement in the body of the loop.

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For example:

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Test	Result
say_spam(1) 🔗	Spam! 🔗
say_spam(2) 🔗	Spam! Spam! 🔗
say_spam(5) 🔗	Spam! Spam! Spam! Spam! Spam! 🔗

====
from unittest.gui import TestCaseGui
import StringIO
import sys

class myTests(TestCaseGui):

def test1(self):
    teststdout = StringIO.StringIO()
    sys.stdout = teststdout
    say_spam(1)
    sys.stdout = sys.__stdout__
    self.assertEqual(teststdout.getvalue(), "Spam!\n", "say_spam(1)")

def test2(self):
    teststdout = StringIO.StringIO()
    sys.stdout = teststdout
    say_spam(2)
    sys.stdout = sys.__stdout__
    self.assertEqual(teststdout.getvalue(), "Spam!\nSpam!\n", "say_spam(2)")

def test3(self):
    teststdout = StringIO.StringIO()
    sys.stdout = teststdout
    say_spam(5)
    sys.stdout = sys.__stdout__
    self.assertEqual(teststdout.getvalue(), "Spam!\nSpam!\nSpam!\nSpam!\nSpam!\n", "say_spam(5)")

def test4(self):
    teststdout = StringIO.StringIO()
    sys.stdout = teststdout
    say_spam(8)
    sys.stdout = sys.__stdout__
    self.assertEqual(teststdout.getvalue(), "Spam!\nSpam!\nSpam!\nSpam!\nSpam!\nSpam!\nSpam!\nSpam!\n", "say_spam(8)")

myTests().main()

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9. Print Integers Less Than n.

Write a function, print_integers_less_than(⁠n), which takes an integer parameter n and prints each integer k which is at least 0 and is less than n, in ascending order.

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Hint: use a simple for loop.

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For example:

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Test	Result
print_integers_less_than(2) 🔗	0 1 🔗
print_integers_less_than(5) 🔗	0 1 2 3 4 🔗
print_integers_less_than(-3) 🔗	🔗

====
from unittest.gui import TestCaseGui
import StringIO
import sys

class myTests(TestCaseGui):
  def test1(self):
    teststdout = StringIO.StringIO()
    sys.stdout = teststdout
    print_integers_less_than(2)
    sys.stdout = sys.__stdout__
    self.assertEqual(teststdout.getvalue(), "0\n1\n", "print_integers_less_than(2)")

def test2(self):
    teststdout = StringIO.StringIO()
    sys.stdout = teststdout
    print_integers_less_than(5)
    sys.stdout = sys.__stdout__
    self.assertEqual(teststdout.getvalue(), "0\n1\n2\n3\n4\n", "print_integers_less_than(5)")

def test3(self):
    teststdout = StringIO.StringIO()
    sys.stdout = teststdout
    print_integers_less_than(-3)
    sys.stdout = sys.__stdout__
    self.assertEqual(teststdout.getvalue(), "", "print_integers_less_than(-3)")

def test4(self):
    teststdout = StringIO.StringIO()
    sys.stdout = teststdout
    print_integers_less_than(0)
    sys.stdout = sys.__stdout__
    self.assertEqual(teststdout.getvalue(), "", "print_integers_less_than(0)")

def test5(self):
    teststdout = StringIO.StringIO()
    sys.stdout = teststdout
    print_integers_less_than(1)
    sys.stdout = sys.__stdout__
    self.assertEqual(teststdout.getvalue(), "0\n", "print_integers_less_than(1)")

def test6(self):
    teststdout = StringIO.StringIO()
    sys.stdout = teststdout
    print_integers_less_than(11)
    sys.stdout = sys.__stdout__
    self.assertEqual(teststdout.getvalue(), "0\n1\n2\n3\n4\n5\n6\n7\n8\n9\n10\n", "print_integers_less_than(11)")

def test7(self):
    teststdout = StringIO.StringIO()
    sys.stdout = teststdout
    print_integers_less_than(15)
    sys.stdout = sys.__stdout__
    self.assertEqual(teststdout.getvalue(), "0\n1\n2\n3\n4\n5\n6\n7\n8\n9\n10\n11\n12\n13\n14\n", "print_integers_less_than(15)")

myTests().main()

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10. Print Perfect Cubes.

Write a function, print_perfect_cubes(n), that takes an integer parameter n and prints the perfect cubes starting from \(0^3 = 0\) and ending with \(n^3\text{.}\) When n is negative, the function prints nothing; but do not check for this condition with an "if" statement, it is unnecessary; use a for loop that will automatically print nothing when \(n < 0\text{.}\)

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Hint for choosing the right range for your for loop: In the general case, when n is not negative, your function will need to print n+1 different values.

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Hint for printing the first part of the output: Convert n to a string and then concatenate that string with "^3"; assign the result to a variable, the_cube. Make the_cube the first argument in your print function call.

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For example:

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Test	Result
print_perfect_cubes(2) 🔗	0^3 = 0 1^3 = 1 2^3 = 8 🔗
print_perfect_cubes(5) 🔗	0^3 = 0 1^3 = 1 2^3 = 8 3^3 = 27 4^3 = 64 5^3 = 125 🔗
print_perfect_cubes(-10) 🔗	🔗

====
from unittest.gui import TestCaseGui
import StringIO
import sys

class myTests(TestCaseGui):

def test1(self):
    teststdout = StringIO.StringIO()
    sys.stdout = teststdout
    print_perfect_cubes(2)
    sys.stdout = sys.__stdout__
    self.assertEqual(teststdout.getvalue(), "0^3 = 0\n1^3 = 1\n2^3 = 8\n", "print_perfect_cubes(2)")

def test2(self):
    teststdout = StringIO.StringIO()
    sys.stdout = teststdout
    print_perfect_cubes(5)
    sys.stdout = sys.__stdout__
    self.assertEqual(teststdout.getvalue(), '0^3 = 0\n1^3 = 1\n2^3 = 8\n3^3 = 27\n4^3 = 64\n5^3 = 125\n', "print_perfect_cubes(5)")

def test3(self):
    teststdout = StringIO.StringIO()
    sys.stdout = teststdout
    print_perfect_cubes(-10)
    sys.stdout = sys.__stdout__
    self.assertEqual(teststdout.getvalue(), "", "print_perfect_cubes(-10)")

def test4(self):
    teststdout = StringIO.StringIO()
    sys.stdout = teststdout
    print_perfect_cubes(1)
    sys.stdout = sys.__stdout__
    self.assertEqual(teststdout.getvalue(), "0^3 = 0\n1^3 = 1\n", "print_perfect_cubes(1)")

def test5(self):
    teststdout = StringIO.StringIO()
    sys.stdout = teststdout
    print_perfect_cubes(9)
    sys.stdout = sys.__stdout__
    self.assertEqual(teststdout.getvalue(), "0^3 = 0\n1^3 = 1\n2^3 = 8\n3^3 = 27\n4^3 = 64\n5^3 = 125\n6^3 = 216\n7^3 = 343\n8^3 = 512\n9^3 = 729\n", "print_perfect_cubes(9)")

def test6(self):
    teststdout = StringIO.StringIO()
    sys.stdout = teststdout
    print_perfect_cubes(13)
    sys.stdout = sys.__stdout__
    self.assertEqual(teststdout.getvalue(), "0^3 = 0\n1^3 = 1\n2^3 = 8\n3^3 = 27\n4^3 = 64\n5^3 = 125\n6^3 = 216\n7^3 = 343\n8^3 = 512\n9^3 = 729\n10^3 = 1000\n11^3 = 1331\n12^3 = 1728\n13^3 = 2197\n", "print_perfect_cubes(13)")

myTests().main()

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CS 220 Python Programming Exercises

Section 1.3 HW2

Exercises Exercises

1. Flip Sign and Add Three.

2. Calculate the Ratio as a Percentage.

3. Rounded Square Root.

4. Round Float.

5. Integer Division and Remainder.

6. Bookcases.

7. Detect Even/Odd.

8. Spam, N Times.

9. Print Integers Less Than n.

10. Print Perfect Cubes.