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CSE 160 Section 2

Loops and Range!

TA1 & TA2

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Logistics

How was HW0? Everything has been set up?

Coding Practice 1 (due Friday January 17)

Coding Practice 2 (due Wednesday January 22)

HW1 (due Friday January 17) expressions, printing, loops

Submitting on Gradescope
Wait for autograder!

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Hw 1 Tips

Watch out for formatting errors - flake8
Your output should exactly match the expected output.

(blanks should be replaced with your answers)

Diffchecker.com

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Lecture Review: Loops

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Loops

Any variable name can be used in place of i (for good style, pick a variable name that fits the context)
Indentation is a requirement to indicate loop body

for i in [0, 1, 2, 3]:

print(i)

PythonTutor

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Loops

Avoid redundancy
More readable
Avoid bugs
Can easily make changes in code body,

or number of times loop is repeated

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Lecture Review: Range

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Range

range(start, stop, step)
range(start, stop)

(inclusive, exclusive)
Step is assumed to be 1

range(stop)

(exclusive)
Step is assumed to be 1; Start is assumed to be 0

Example: range(0, 6, 2) loops through [0, 2, 4]

Equivalent to: range(0, 5, 2)

Python Tutor

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Kahoot!

Link

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Section Handout Problems

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Lists, Ranges, and Loops

3. What is the output printed by the following program?

for value in [1, 3, 5]:

print(value + value ** 2)

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Lists, Ranges, and Loops

3. What is the output printed by the following program?

for value in [1, 3, 5]:

print(value + value ** 2)

Output:

2

12

30

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Lists, Ranges, and Loops

4. Write a for loop that will print the result of multiplying 3 by the numbers 8 through 12.

The example solution is two lines long. Your output should read:

24

27

30

33

36

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Lists, Ranges, and Loops

4. Possible solutions appear below:

for value in [8, 9, 10, 11, 12]:

print(3 * value)

for value in range(8, 13):

print(3 * value)

for value in range(24, 37, 3):

print(value)

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Nested Loops

5. What is the output printed by the following program?

for i in [1, 2, 3]:

for j in [1, 2, 3]:

print(i + j)

Answer: Python Tutor

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Nested Loops

6. What is the output printed by the following program?

sum = 0

for i in [1, 2, 3]:

for j in [1, 2, 3]:

sum = sum + i

print(sum)

Answer: Python Tutor

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Nested Loops

8. Write code to print the number of people over 20 years old in the list ages

ages = [20, 21, 20, 22, 19, 18, 14, 35]

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Nested Loops

8. Write code to print the number of people over 20 years old in the list ages

ages = [20, 21, 20, 22, 19, 18, 14, 35]

count = 0;

for age in ages:

if (age > 20):� count += 1;

print(count)

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Mod Operator Overview

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Mod

Modulo operator, denoted as %, is a mathematical operation that calculates the remainder when one number is divided by another.

2 % 5

3 % 7

5 % 2

8 % 3

20 % 5

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Mod

2 % 5 = 2

3 % 7 = 3

5 % 2 = 1

8 % 3 = 2

20 % 5 = 0

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Mod

What is the output of the following code?

for i in range(5):

print(i % 3)

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Mod

What is the output of the following code?

for i in range(5):

print(i % 3)

Answer:

0

1

2

0

1

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If / Else Overview

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If/ Else Structure

Checks that condition is True/False, and executing code based on that condition

is_raining = True

is_sprinkling = False

if is_raining:

print(“Bring an umbrella”)

elif is_sprinkling:

print(“Bring a raincoat”)

else:

print(“Bring sunglasses”)

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If/ Else Structure

Checks that condition is True/False, and executing code based on that condition

is_raining = True

is_sprinkling = False

if is_raining:

print(“Bring an umbrella”)

elif is_sprinkling:

print(“Bring a raincoat”)

else:

print(“Bring sunglasses”)

Output:

Bring an umbrella

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Coding Practice 1

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# ~~~ Begin Problem 1 ~~~

'''

Given a list of integers, prints the sum of the even ints in the list.

Note: the % "mod" operator computes the remainder, e.g. 5 % 2 is 1.

Assumptions:

nums: a variable containing list of integers.

Prints: a integer representing the sum of the even numbers in the list

Examples:

nums = [5, 2, 6, 3, 4] should print 12

nums = [3, 6, 11, 2, 5] should print 8

nums = [] should print 0

nums = [7] should print 0

nums = [5, 8, 5] should print 8

nums = [72, 2, 6, 1] should print 80

nums = [6] should print 6

nums = [4, 4, 4] should print 12

nums = [1, 1, 1, 2] should print 2

Try copying these values into the nums variable to see if your code works.

'''

nums = []

sum = 0

# Write your code for Problem 1 here!

print(sum)

# ~~~ End Problem 1 ~~~

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Section Code

** Note that section codes are only given in-person and are not given through email, Ed, or other mediums.