CS 149
Professor: Alvin Chao
20/5 - 7 + 5*3 - 3
20//5 - 9 + 5*3 - 3
The answer is the number of people out of 10 that will have issues with this problem.
Variables and Expressions
Thonny Shell - Variables + Assignments
Enter the following into a Python Shell in Thonny: Red lines have errors https://strawpoll.com/e7ZJGvQ3vy3
input("enter the mass in grams: ")
mass = input("enter another mass in grams: ")
mass
unit = input("enter the units for mass: ")
print(mass, unit)
ten = 10
print(ten / 2)
abs( - 1)
abs(-1 * 10)�data = 12
data
Data
Data = 34
data
Data
my data = 56
My_data = 78�3data = "hello"
data3 = "world"
data3 = hello
mass = 273 + 100
273 + 100 = mass
mass
Mass + 100
mass -100
Why use float versus int
1. Identify the Python keyword used in a variable declaration to indicate
a) an integer:� b) a floating-point number:
2. Consider numbers of dollar bills, cents, and grams. Which of these units only makes sense as an integer, and why?
3. What would you expect the following statements to print out?
a) print(dollars)
b) print(cents)
c) print(grams)
4. Which side of the equals sign (left or right) was assigned a new value?
5. In your own words, explain how you should read the = sign in Python.For example,the Python statement x = a + b should be read as “x _____ a plus b.”
dollars = int(3)
cents = int(90)
grams = float(3)
Float vs int
For the following questions, assume you have these two variables:
int(x) = 0 �float(y) = 0.0
Questions (10 min)
6. What operator has the lowest precedence?Why do you think Python is designed that way?
7. The + and - operators show up twice in the table of operator precedence. For the Python expression x = 5 * -3; explain how you know whether the - operator is being used as an unary or binary operator in this expression.
y = 9 / 2 versus y = 9 // 2
Division
14. / 4. | Evaluates to | |
14. / 4 | Evaluates to | |
14 / 4. | Evaluates to | |
14 / 4 | Evaluates to | |
Floor / regular / remainder division
9 // 4 evaluates to 2 9 / 4.0 evaluates to 2.25 9 % 4 evaluates to 1
10 // 4 evaluates to 2 10 / 4.0 evaluates to 2.5 10 % 4 evaluates to 2
11 // 4 evaluates to 2 11. / 4 evaluates to 2.75 11 % 4 evaluates to 3
12 // 4 evaluates to 3 12 / 4.0 evaluates to 3.0 12 % 4 evaluates to 0
13 // 4 evaluates to 3 13 / 4. evaluates to 3.25 13 % 4 evaluates to 1
14 // 4 evaluates to 3 14.0 / 4 evaluates to 3.5 14 % 4 evaluates to 2
15 // 4 evaluates to 3 15 / 4.0 evaluates to 3.75 15 % 4 evaluates to 3
16 // 4 evaluates to 4 16 / 4. evaluates to 4.0 16 % 4 evaluates to 0
Output
Single line output
# Including end=' ' keeps output on same line
print('Hello,', end=' ')�print('this text is all', end=' ')
print('on one line.')
Multiple items in one print
age = 20�print('You are', age, 'years old.')
Calculations in a print statement
age = 20�print('Next year you will be', age + 1, 'years old.')
Strings and operators
first = "James"
last = "Madison"
full = first + last
quad = first * 4
print(first + last)
print(first, last)
print(first * 4)
print(full)
print(quad)
8.What is the output of these statements:
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