Practice Exercises for Variables and Assignments#

Given a template that pre-defines a variable miles, write an assignment statement that defines a variable feet whose value is the number of feet in miles miles. Miles to feet template — Miles to feet solution — Miles to feet (Checker)
```
miles = 13
miles = 57
miles = 82.67
feet = miles * 5280
print(f'{miles} miles equals {feet} feet.')
```
- In Python3 you do not need to convert integers to strings.
- f-strings in Python3 are very convenient compared to concatenating strings using +
Given a template that pre-defines three variables hours, minutes and seconds, write an assignment statement that updates the variable total_seconds to have a value corresponding to the total number of seconds for hours hours, minutes minutes and seconds seconds. Hours to second template — Hours to second solution — Hours to second (Checker)
```
hours = 7
minutes = 21
seconds = 37

total_seconds = (hours * 60 + minutes) * 60 + seconds
print(f'{hours} hours, {minutes} minutes, and {seconds} seconds totals to',
      f'{total_seconds} seconds')
```
Given a template that pre-defines the variables width and height that are the lengths of the sides of a rectangle, write an assignment statement that defines a variable perimeter whose value is the perimeter of the rectangle in inches. Perimeter of rectangle template — Perimeter of rectangle solution — Perimeter of rectangle (Checker)
```
width = 4
height = 7

perimeter = (width + height)*2
print(f'A rectangle {width} inches wide and {height} inches high has a perimeter of {perimeter} inches.')
```
Given a template that pre-defines the variables width and height that are the lengths of the sides of a rectangle, write an assignment statement that defines a variable area whose value is the area of the rectangle in square inches. Area of rectangle template — Area of rectangle solution — Area of rectangle (Checker)
```
width = 4
height = 7

area = width * height

print(area)
```
Given a template that pre-defines the constant PI and the variable radius corresponding to the radius of a circle in inches, write an assignment statement that defines a variable circumference whose value is the circumference of a circle with radius radius in inches. Circumference of circle template — Circumference of circle solution — Circumference of circle (Checker)
```
PI = 3.14
radius = 8

circumference = 2 * PI * radius
print(circumference)
```
Given a template that pre-defines the constant PI and the variable radius corresponding to the radius of a circle in inches, write an assignment statement that defines a variable area whose value is the area of a circle with radius radius in square inches. Area of circle template — Area of circle solution — Area of circle (Checker)
```
PI = 3.14
radius = 8

area = PI * radius**2
print(area)
```
Given the pre-defined variables present_value, annual_rate and years, write an assignment statement that define a variable future_value whose value is present_value dollars invested at annual_rate percent interest, compounded annually for years years. Future value template — Future value solution — Future value (Checker)
```
present_value = 1000
annual_rate = 7
years = 10
future_value = present_value * (1 + 0.01 * 7)**10

print(future_value)
```
Give the pre-defined variables first_name and last_name, write an assignment statement that defines the variable name_tag whose value is the string “My name is % %.” where the percents should be replaced by first_name and last_name. Note that, in Python, you can use the + operator on strings to concatenate (i.e. join) them together into a single string. Name tag template — Name tag solution — Name tag (Checker)
```
first_name = "Joe"
last_name = "Warren"

name_tag = f'My name is {first_name} {last_name}'
print(name_tag)

name_tag = 'My name is ' + first_name + ' ' + last_name
print(name_tag)

name_tag = 'My name is', first_name, last_name
print(*name_tag)  # argument list unpacking
```
- You can also use f-strings
- if you use + then pay attention to spaces, because + concatenates the strings without any spaces in between.
- also argument list unpacking possible
Given the pre-defined variables name (a string) and age (a number), write an assignment statement that defines a variable statement whose value is the string "% is % years old." where the percents should be replaced by name and the string form of age. Name and age template — Name and age solution — Name and age (Checker)
```
name = "Joe Warren"
age = 52

statement = f'{name} is {age} years old'
print(statement)
```
Given the variables x0, y0, x1, and y1, write an assignment statement that defines a variable distance whose values is the distance between the points $(x0,y0)$ and $(x1, y1)$. Point distance template — Point distance solution — Point distance (Checker)
```
x0 = 2
y0 = 2
x1 = 5
y1 = 6

distance = ( (x0 - y0)**2 + (x1 - y1)**2 )**.5
print(distance)
```
Challenge: Heron’s formula states the area of a triangle is $\sqrt{s(s-a)(s-b)(s-c)}$ where $a$, $b$ and $c$ are the lengths of the sides of the triangle and $s = \frac{1}{2}(a + b +c)$ is thesemi-perimeterof the triangle. Given the variables x0, y0, x1,y1, x2, and y2, write a Python program that computes a variable area whose value is the area of the triangle with vertices $(x0,y0)$, $(x1, y1)$ and $(x2, y2)$. (Hint: our solution uses five assignment statements.) Triangle area template — Triangle area solution — Triangle area (Checker)
```
x0, y0 = 0, 0
x1, y1 = 3, 4
x2, y2 = 1, 1

a = ( (x0 - x1)**2 + (y0 - y1)**2 )**.5
b = ( (x1 - x2)**2 + (y1 - y2)**2 )**.5
c = ( (x2 - x0)**2 + (y2 - y0)**2 )**.5
s = (a + b + c)/2
area = (s * (s-a) * (s-b) * (s-c))**.5
print(area)
```