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Lec11 update

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s23/Gurmail_lecture_notes/11_Iteration-2/lec_11_Iteration_2.ipynb
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%% Cell type:markdown id:5117857a tags:
# Announcements - Friday
* Download files for today's lecture
* Quiz 3 due today
* P4 Bad Link
* [Thank You](https://docs.google.com/forms/d/e/1FAIpQLSe0Zi6JFbxPIEVr7u1DJykuel-qSi7U0sBp2iR0gi6R_CArgw/viewform)
* [Regrade request procedure](https://piazza.com/class/ld8bqui1lgeas/post/105)
* Exam 1
* Number 2 pencil
* Room assignment via Canvas Message (before Tuesday)
* [Exam 1 Conflict Form](https://docs.google.com/forms/d/e/1FAIpQLScKmey733tOjLfJ2q13Np76w_4o6cFcGVyNqWZmseZH0KNp2w/viewform)
* one page note sheet
* put anything you want on this sheet
* we will keep this sheet - make a copy if you want one
* ID Card and #2 pencil
* General: Wednesday February 22: 5:45 pm
* McBurney: Wednesday Februrary 22 5:30 pm - If you are approved for anything other than extra time and small group testing please fill out the form
* Alternate: Thursday February 23 5:45 pm
* Location will be sent by email on Monday February 20
* Note: Chemistry has an exam at the same time as our Wednesday exam
* Note: Wednesday Evening section
- alternate time 7:30 - 9:00 pm
- please fill out the conflict form to get on the list for the location email
- feel free to revise your conflict form if this time works better for you
* [The best way to study for the exam!!!](https://git.doit.wisc.edu/cdis/cs/courses/cs220/cs220-lecture-material/-/tree/main/s23/old_exams/exam1)
%% Cell type:markdown id:1fd5544f tags: %% Cell type:markdown id:1fd5544f tags:
# Iteration 2 # Iteration 2
## Readings: ## Readings:
- Chapter 2 of Sweigart book - Chapter 2 of Sweigart book
- Chapter 6.4 of Python for Everybody - Chapter 6.4 of Python for Everybody
%% Cell type:code id:e15b9d08 tags: %% Cell type:code id:e15b9d08 tags:
``` python ``` python
import math import math
``` ```
%% Cell type:markdown id:ebce36a5 tags: %% Cell type:markdown id:ebce36a5 tags:
## Learning Objectives ## Learning Objectives
- Read and trace through Python code containing nested loops. - Read and trace through Python code containing nested loops.
- Read and trace through Python code using `break` or `continue` in a `while` loop - Read and trace through Python code using `break` or `continue` in a `while` loop
- Determine the effect of break and continue in nested loops - Determine the effect of break and continue in nested loops
%% Cell type:markdown id:8f91daea tags: %% Cell type:markdown id:8f91daea tags:
## `break` example ## `break` example
- `break` enables to terminate execution of a while loop - `break` enables to terminate execution of a while loop
- typically used with a conditional; that is you break when condition evaluates to `True` - typically used with a conditional; that is you break when condition evaluates to `True`
%% Cell type:code id:5ec2099a tags: %% Cell type:code id:5ec2099a tags:
``` python ``` python
def is_prime(num): def is_prime(num):
""" returns True if x is prime, false otherwise. """ returns True if x is prime, false otherwise.
Assumes x is positive""" Assumes x is positive"""
# try all divisors from 2 to sqrt(num) to check if num is prime # try all divisors from 2 to sqrt(num) to check if num is prime
divisor = 2 divisor = 2
while divisor <= math.sqrt(num): while divisor <= math.sqrt(num):
# check if num is divisible by divisor # check if num is divisible by divisor
if num % divisor == 0: if num % divisor == 0:
return False return False
divisor += 1 divisor += 1
return True return True
``` ```
%% Cell type:code id:18f5a22c tags: %% Cell type:code id:18f5a22c tags:
``` python ``` python
print(is_prime(1)) print(is_prime(1))
print(is_prime(2)) print(is_prime(2))
print(is_prime(3)) print(is_prime(3))
print(is_prime(7)) print(is_prime(7))
print(is_prime(16)) print(is_prime(16))
print(is_prime(23)) print(is_prime(23))
print(is_prime(1000000)) print(is_prime(1000000))
``` ```
%% Output %% Output
True True
True True
True True
True True
False False
True True
False False
%% Cell type:code id:daca8575 tags: %% Cell type:code id:daca8575 tags:
``` python ``` python
def has_prime(start, end): def has_prime(start, end):
found_prime = False found_prime = False
num = start num = start
while num <= end: while num <= end:
if is_prime(num): if is_prime(num):
print(num) print(num)
found_prime = True found_prime = True
# As soon as you find the first prime, your work # As soon as you find the first prime, your work
# here is done, hence the break out of the loop! # here is done, hence the break out of the loop!
break break
num += 1 num += 1
return found_prime return found_prime
``` ```
%% Cell type:code id:0f7bd5ca tags: %% Cell type:code id:0f7bd5ca tags:
``` python ``` python
has_prime(14, 16) has_prime(14, 16)
``` ```
%% Output %% Output
False False
%% Cell type:code id:4fd676f3 tags: %% Cell type:code id:4fd676f3 tags:
``` python ``` python
has_prime(1000000, 1001000) has_prime(1000000, 1001000)
``` ```
%% Output %% Output
1000003 1000003
True True
%% Cell type:markdown id:dfc74fed tags: %% Cell type:markdown id:dfc74fed tags:
## `continue` example ## `continue` example
- `continue` enables to move on to the next iteration of the while loop - `continue` enables to move on to the next iteration of the while loop
- typically used with a conditional; that is you continue when condition evaluates to `True` - typically used with a conditional; that is you continue when condition evaluates to `True`
%% Cell type:code id:e90b47b5 tags: %% Cell type:code id:e90b47b5 tags:
``` python ``` python
total = 0 # sum total = 0 # sum
count = 0 count = 0
while True: while True:
#Handle "q" input for quitting #Handle "q" input for quitting
age = input("Enter an age [0-100]: ") age = input("Enter an age [0-100]: ")
if age == "q": if age == "q":
break break
age = float(age) age = float(age)
if age < 0 or age > 100: if age < 0 or age > 100:
print("Bad input!") print("Bad input!")
continue continue
total += age total += age
count += 1 count += 1
print("Average age of user so far is: ", total / count) print("Average age of user so far is: ", total / count)
``` ```
%% Output %% Output
Enter an age [0-100]: 10 Enter an age [0-100]: 10
Average age of user so far is: 10.0 Average age of user so far is: 10.0
Enter an age [0-100]: 20 Enter an age [0-100]: 20
Average age of user so far is: 15.0 Average age of user so far is: 15.0
Enter an age [0-100]: 102 Enter an age [0-100]: 102
Bad input! Bad input!
Enter an age [0-100]: q Enter an age [0-100]: q
%% Cell type:markdown id:8b037e4f tags: %% Cell type:markdown id:8b037e4f tags:
### After lecture ### After lecture
%% Cell type:markdown id:bf87a5ac tags: %% Cell type:markdown id:bf87a5ac tags:
How many times is the *while loop condition line* executed? How many times is the *while loop condition line* executed?
%% Cell type:code id:cb6bb684 tags: %% Cell type:code id:cb6bb684 tags:
``` python ``` python
n = 7 n = 7
while n >= 5: while n >= 5:
print(n) print(n)
n -= 1 n -= 1
# Answer is 4. # Answer is 4.
# Loop condition line always gets executed number of # Loop condition line always gets executed number of
# iterations + 1 times. # iterations + 1 times.
``` ```
%% Cell type:markdown id:4def9307 tags: %% Cell type:markdown id:4def9307 tags:
Refactor the below function. Refactor the below function.
%% Cell type:code id:9421ad49 tags: %% Cell type:code id:9421ad49 tags:
``` python ``` python
def is_between(a, b, c): def is_between(a, b, c):
"""Return True if b is between a and c (exclusive), """Return True if b is between a and c (exclusive),
False otherwise""" False otherwise"""
if a < c: if a < c:
if a < b and b < c: if a < b and b < c:
return True return True
else: else:
return False return False
elif c <= a: elif c <= a:
if c < b and b < a: if c < b and b < a:
return True return True
else: else:
return False return False
else: else:
return False return False
print(is_between(1, 3, 2)) # False print(is_between(1, 3, 2)) # False
print(is_between(5, 11, 20)) # True print(is_between(5, 11, 20)) # True
print(is_between(20, 3, 5)) # False print(is_between(20, 3, 5)) # False
print(is_between(50, 11, 9)) # True print(is_between(50, 11, 9)) # True
print(is_between(4, 4, 4)) # False print(is_between(4, 4, 4)) # False
``` ```
%% Output %% Output
False False
True True
False False
True True
False False
%% Cell type:code id:21951d05 tags: %% Cell type:code id:21951d05 tags:
``` python ``` python
def is_between_v2(a, b, c): def is_between_v2(a, b, c):
return a < b < c or c < b < a return a < b < c or c < b < a
print(is_between_v2(1, 3, 2)) # False print(is_between_v2(1, 3, 2)) # False
print(is_between_v2(5, 11, 20)) # True print(is_between_v2(5, 11, 20)) # True
print(is_between_v2(20, 3, 5)) # False print(is_between_v2(20, 3, 5)) # False
print(is_between_v2(50, 11, 9)) # True print(is_between_v2(50, 11, 9)) # True
print(is_between_v2(4, 4, 4)) # False print(is_between_v2(4, 4, 4)) # False
``` ```
%% Output %% Output
False False
True True
False False
True True
False False
%% Cell type:markdown id:0f71dc12 tags: %% Cell type:markdown id:0f71dc12 tags:
Trace the output without using Python interpreter Trace the output without using Python interpreter
%% Cell type:code id:b942d01f tags: %% Cell type:code id:b942d01f tags:
``` python ``` python
x = 1 x = 1
while x < 5: while x < 5:
y = 1 y = 1
while y < 10: while y < 10:
print (x * y, "\t", end="") print (x * y, "\t", end="")
y += 1 y += 1
print() print()
x += 1 x += 1
``` ```
%% Cell type:code id:7743e03b tags: %% Cell type:code id:7743e03b tags:
``` python ``` python
width = 9 width = 9
height = 4 height = 4
symbol = '#' symbol = '#'
row = 0 row = 0
while row < height: while row < height:
col = 0 col = 0
if row % 2 == 1: if row % 2 == 1:
print(" ", end="") print(" ", end="")
while col < width: while col < width:
print(symbol + ' ', end="") print(symbol + ' ', end="")
col += 1 col += 1
# displays just a newline # displays just a newline
print() # recall default value for end parameter is "\n" print() # recall default value for end parameter is "\n"
row += 1 row += 1
``` ```
......
s23/Gurmail_lecture_notes/11_Iteration-2/lec_11_Iteration_2_template.ipynb → s23/Gurmail_lecture_notes/11_Iteration-2/lec_11_Iteration_2_template_Gurmail_lec1.ipynb
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− 0
View file @ 998a8a33
%% Cell type:markdown id:e6f081e5 tags:
# Announcements - Friday
* Download files for today's lecture
* Quiz 3 due today
* P4 Bad Link
* [Thank You](https://docs.google.com/forms/d/e/1FAIpQLSe0Zi6JFbxPIEVr7u1DJykuel-qSi7U0sBp2iR0gi6R_CArgw/viewform)
* [Regrade request procedure](https://piazza.com/class/ld8bqui1lgeas/post/105)
* Exam 1
* Number 2 pencil
* Room assignment via Canvas Message (before Tuesday)
* [Exam 1 Conflict Form](https://docs.google.com/forms/d/e/1FAIpQLScKmey733tOjLfJ2q13Np76w_4o6cFcGVyNqWZmseZH0KNp2w/viewform)
* one page note sheet
* put anything you want on this sheet
* we will keep this sheet - make a copy if you want one
* ID Card and #2 pencil
* General: Wednesday February 22: 5:45 pm
* McBurney: Wednesday Februrary 22 5:30 pm - If you are approved for anything other than extra time and small group testing please fill out the form
* Alternate: Thursday February 23 5:45 pm
* Location will be sent by email on Monday February 20
* Note: Chemistry has an exam at the same time as our Wednesday exam
* Note: Wednesday Evening section
- alternate time 7:30 - 9:00 pm
- please fill out the conflict form to get on the list for the location email
- feel free to revise your conflict form if this time works better for you
* [The best way to study for the exam!!!](https://git.doit.wisc.edu/cdis/cs/courses/cs220/cs220-lecture-material/-/tree/main/s23/old_exams/exam1)
%% Cell type:markdown id:cce4a7bf tags: %% Cell type:markdown id:cce4a7bf tags:
# Iteration 2 # Iteration 2
## Readings: ## Readings:
- Chapter 2 of Sweigart book - Chapter 2 of Sweigart book
- Chapter 6.4 of Python for Everybody - Chapter 6.4 of Python for Everybody
%% Cell type:code id:7693263d tags: %% Cell type:code id:7693263d tags:
``` python ``` python
import math import math
``` ```
%% Cell type:markdown id:0b7e0914 tags: %% Cell type:markdown id:0b7e0914 tags:
## Learning Objectives ## Learning Objectives
- Read and trace through Python code containing nested loops. - Read and trace through Python code containing nested loops.
- Read and trace through Python code using `break` or `continue` in a `while` loop - Read and trace through Python code using `break` or `continue` in a `while` loop
- Determine the effect of break and continue in nested loops - Determine the effect of break and continue in nested loops
%% Cell type:markdown id:06b520a0 tags: %% Cell type:markdown id:06b520a0 tags:
## `break` example ## `break` example
- `break` enables to terminate execution of a while loop - `break` enables to terminate execution of a while loop
- typically used with a conditional; that is you break when condition evaluates to `True` - typically used with a conditional; that is you break when condition evaluates to `True`
%% Cell type:code id:8067fa3e tags: %% Cell type:code id:8067fa3e tags:
``` python ``` python
def is_prime(num): def is_prime(num):
""" returns True if x is prime, false otherwise. """ returns True if x is prime, false otherwise.
Assumes x is positive""" Assumes x is positive"""
# try all divisors from 2 to sqrt(num) to check if num is prime # try all divisors from 2 to sqrt(num) to check if num is prime
divisor = ??? divisor = ???
while ???: while ???:
# check if num is divisible by divisor # check if num is divisible by divisor
if num % divisor == ???: if num % divisor == ???:
return ??? return ???
divisor ??? divisor ???
return ??? return ???
``` ```
%% Cell type:code id:2e3d3f29 tags: %% Cell type:code id:2e3d3f29 tags:
``` python ``` python
print(is_prime(1)) print(is_prime(1))
print(is_prime(2)) print(is_prime(2))
print(is_prime(3)) print(is_prime(3))
print(is_prime(7)) print(is_prime(7))
print(is_prime(16)) print(is_prime(16))
print(is_prime(23)) print(is_prime(23))
print(is_prime(1000000)) print(is_prime(1000000))
``` ```
%% Cell type:code id:9a28c726 tags: %% Cell type:code id:9a28c726 tags:
``` python ``` python
def has_prime(start, end): def has_prime(start, end):
# TODO: write a for loop using range, to: # TODO: write a for loop using range, to:
# 1. iterate over every number from start to end # 1. iterate over every number from start to end
# 2. call is_prime function, to determine if it is prime # 2. call is_prime function, to determine if it is prime
# 3. if you find at least one prime, has_prime should # 3. if you find at least one prime, has_prime should
# return True, False otherwise # return True, False otherwise
pass pass
``` ```
%% Cell type:code id:5cde0776 tags: %% Cell type:code id:5cde0776 tags:
``` python ``` python
has_prime(14, 16) has_prime(14, 16)
``` ```
%% Cell type:code id:3a5be934 tags: %% Cell type:code id:3a5be934 tags:
``` python ``` python
has_prime(1000000, 1001000) has_prime(1000000, 1001000)
``` ```
%% Cell type:markdown id:12c14f3b tags: %% Cell type:markdown id:12c14f3b tags:
## `continue` example ## `continue` example
- `continue` enables to move on to the next iteration of the while loop - `continue` enables to move on to the next iteration of the while loop
- typically used with a conditional; that is you continue when condition evaluates to `True` - typically used with a conditional; that is you continue when condition evaluates to `True`
%% Cell type:code id:ef8d6e0b tags: %% Cell type:code id:ef8d6e0b tags:
``` python ``` python
# TODO: write an infinite loop using while # TODO: write an infinite loop using while
# TODO: get user input for age # TODO: get user input for age
# Goal: to compute running average # Goal: to compute running average
# It is easy to keep track of total and number of user # It is easy to keep track of total and number of user
# inputs to compute running average # inputs to compute running average
# TODO: discuss what is acceptable range for age # TODO: discuss what is acceptable range for age
# What is the guinness world record for oldest person? # What is the guinness world record for oldest person?
# TODO: discuss where you will initialize variables to keep track # TODO: discuss where you will initialize variables to keep track
# of total and number of user inputs so far and then type the # of total and number of user inputs so far and then type the
# computation lines to compute updated total and running average # computation lines to compute updated total and running average
# Now, try entering input as a large number outside of your # Now, try entering input as a large number outside of your
# acceptable age range. What happens to your average? # acceptable age range. What happens to your average?
# TODO: handle this by writing a conditional and use continue, # TODO: handle this by writing a conditional and use continue,
# when user enters invalid age # when user enters invalid age
# Finally, how do we terminate the infinite while loop # Finally, how do we terminate the infinite while loop
# Let's accept "q" as user input for termination # Let's accept "q" as user input for termination
# TODO: handle that using another conditional # TODO: handle that using another conditional
# Think carefully about where this conditional needs to be in # Think carefully about where this conditional needs to be in
# terms of control flow # terms of control flow
``` ```
%% Cell type:markdown id:944cc596 tags: %% Cell type:markdown id:944cc596 tags:
### After lecture ### After lecture
%% Cell type:markdown id:0820ba66 tags: %% Cell type:markdown id:0820ba66 tags:
How many times is the *while loop condition line* executed? How many times is the *while loop condition line* executed?
%% Cell type:code id:c3c14b7b tags: %% Cell type:code id:c3c14b7b tags:
``` python ``` python
n = 7 n = 7
while n >= 5: while n >= 5:
print(n) print(n)
n -= 1 n -= 1
# Answer is 4. # Answer is 4.
# Loop condition line always gets executed number of # Loop condition line always gets executed number of
# iterations + 1 times. # iterations + 1 times.
``` ```
%% Cell type:markdown id:7cf19523 tags: %% Cell type:markdown id:7cf19523 tags:
Refactor the below function. Refactor the below function.
%% Cell type:code id:a313a32f tags: %% Cell type:code id:a313a32f tags:
``` python ``` python
def is_between(a, b, c): def is_between(a, b, c):
"""Return True if b is between a and c (exclusive), """Return True if b is between a and c (exclusive),
False otherwise""" False otherwise"""
if a < c: if a < c:
if a < b and b < c: if a < b and b < c:
return True return True
else: else:
return False return False
elif c <= a: elif c <= a:
if c < b and b < a: if c < b and b < a:
return True return True
else: else:
return False return False
else: else:
return False return False
print(is_between(1, 3, 2)) # False print(is_between(1, 3, 2)) # False
print(is_between(5, 11, 20)) # True print(is_between(5, 11, 20)) # True
print(is_between(20, 3, 5)) # False print(is_between(20, 3, 5)) # False
print(is_between(50, 11, 9)) # True print(is_between(50, 11, 9)) # True
print(is_between(4, 4, 4)) # False print(is_between(4, 4, 4)) # False
``` ```
%% Cell type:code id:7fd82ae9 tags: %% Cell type:code id:7fd82ae9 tags:
``` python ``` python
def is_between_v2(a, b, c): def is_between_v2(a, b, c):
return ??? return ???
print(is_between_v2(1, 3, 2)) # False print(is_between_v2(1, 3, 2)) # False
print(is_between_v2(5, 11, 20)) # True print(is_between_v2(5, 11, 20)) # True
print(is_between_v2(20, 3, 5)) # False print(is_between_v2(20, 3, 5)) # False
print(is_between_v2(50, 11, 9)) # True print(is_between_v2(50, 11, 9)) # True
print(is_between_v2(4, 4, 4)) # False print(is_between_v2(4, 4, 4)) # False
``` ```
%% Cell type:markdown id:ca9037f7 tags: %% Cell type:markdown id:ca9037f7 tags:
Trace the output without using Python interpreter Trace the output without using Python interpreter
%% Cell type:code id:ec8b1b32 tags: %% Cell type:code id:ec8b1b32 tags:
``` python ``` python
x = 1 x = 1
while x < 5: while x < 5:
y = 1 y = 1
while y < 10: while y < 10:
print (x * y, "\t", end="") print (x * y, "\t", end="")
y += 1 y += 1
print() print()
x += 1 x += 1
``` ```
%% Cell type:code id:74060bc4 tags: %% Cell type:code id:74060bc4 tags:
``` python ``` python
width = 9 width = 9
height = 4 height = 4
symbol = '#' symbol = '#'
row = 0 row = 0
while row < height: while row < height:
col = 0 col = 0
if row % 2 == 1: if row % 2 == 1:
print(" ", end="") print(" ", end="")
while col < width: while col < width:
print(symbol + ' ', end="") print(symbol + ' ', end="")
col += 1 col += 1
# displays just a newline # displays just a newline
print() # recall default value for end parameter is "\n" print() # recall default value for end parameter is "\n"
row += 1 row += 1
``` ```
......
s23/Gurmail_lecture_notes/11_Iteration-2/.ipynb_checkpoints/lec_11_Iteration_2-checkpoint.ipynb → s23/Gurmail_lecture_notes/11_Iteration-2/lec_11_Iteration_2_template_Gurmail_lec2.ipynb
+ 105
− 153
View file @ 998a8a33
%% Cell type:markdown id:1fd5544f tags: %% Cell type:markdown id:e6f081e5 tags:
# Announcements - Friday
* Download files for today's lecture
* Quiz 3 due today
* P4 Bad Link
* [Thank You](https://docs.google.com/forms/d/e/1FAIpQLSe0Zi6JFbxPIEVr7u1DJykuel-qSi7U0sBp2iR0gi6R_CArgw/viewform)
* [Regrade request procedure](https://piazza.com/class/ld8bqui1lgeas/post/105)
* Exam 1
* Number 2 pencil
* Room assignment via Canvas Message (before Tuesday)
* [Exam 1 Conflict Form](https://docs.google.com/forms/d/e/1FAIpQLScKmey733tOjLfJ2q13Np76w_4o6cFcGVyNqWZmseZH0KNp2w/viewform)
* one page note sheet
* put anything you want on this sheet
* we will keep this sheet - make a copy if you want one
* ID Card and #2 pencil
* General: Wednesday February 22: 5:45 pm
* McBurney: Wednesday Februrary 22 5:30 pm - If you are approved for anything other than extra time and small group testing please fill out the form
* Alternate: Thursday February 23 5:45 pm
* Location will be sent by email on Monday February 20
* Note: Chemistry has an exam at the same time as our Wednesday exam
* Note: Wednesday Evening section
- alternate time 7:30 - 9:00 pm
- please fill out the conflict form to get on the list for the location email
- feel free to revise your conflict form if this time works better for you
* [The best way to study for the exam!!!](https://git.doit.wisc.edu/cdis/cs/courses/cs220/cs220-lecture-material/-/tree/main/s23/old_exams/exam1)
%% Cell type:markdown id:cce4a7bf tags:
# Iteration 2 # Iteration 2
## Readings: ## Readings:
- Chapter 2 of Sweigart book - Chapter 2 of Sweigart book
- Chapter 6.4 of Python for Everybody - Chapter 6.4 of Python for Everybody
%% Cell type:code id:e15b9d08 tags: %% Cell type:code id:7693263d tags:
``` python ``` python
import math import math
``` ```
%% Cell type:markdown id:ebce36a5 tags: %% Cell type:markdown id:0b7e0914 tags:
## Learning Objectives ## Learning Objectives
- Read and trace through Python code containing nested loops. - Read and trace through Python code containing nested loops.
- Read and trace through Python code using `break` or `continue` in a `while` loop - Read and trace through Python code using `break` or `continue` in a `while` loop
- Determine the effect of break and continue in nested loops - Determine the effect of break and continue in nested loops
%% Cell type:markdown id:8f91daea tags: %% Cell type:markdown id:06b520a0 tags:
## `break` example ## `break` example
- `break` enables to terminate execution of a while loop - `break` enables to terminate execution of a while loop
- typically used with a conditional; that is you break when condition evaluates to `True` - typically used with a conditional; that is you break when condition evaluates to `True`
%% Cell type:code id:5ec2099a tags: %% Cell type:code id:8067fa3e tags:
``` python ``` python
def is_prime(num): def is_prime(num):
""" returns True if x is prime, false otherwise. """ returns True if x is prime, false otherwise.
Assumes x is positive""" Assumes x is positive"""
# try all divisors from 2 to sqrt(num) to check if num is prime # try all divisors from 2 to sqrt(num) to check if num is prime
divisor = 2 divisor = ???
while divisor <= math.sqrt(num): while ???:
# check if num is divisible by divisor # check if num is divisible by divisor
if num % divisor == 0: if num % divisor == ???:
return False return ???
divisor += 1 divisor ???
return True return ???
``` ```
%% Cell type:code id:18f5a22c tags: %% Cell type:code id:2e3d3f29 tags:
``` python ``` python
print(is_prime(1)) print(is_prime(1))
print(is_prime(2)) print(is_prime(2))
print(is_prime(3)) print(is_prime(3))
print(is_prime(7)) print(is_prime(7))
print(is_prime(16)) print(is_prime(16))
print(is_prime(23)) print(is_prime(23))
print(is_prime(1000000)) print(is_prime(1000000))
``` ```
%% Output %% Cell type:code id:9a28c726 tags:
True
True
True
True
False
True
False
%% Cell type:code id:daca8575 tags:
``` python ``` python
def has_prime(start, end): def has_prime(start, end):
found_prime = False # TODO: write a for loop using range, to:
num = start # 1. iterate over every number from start to end
while num <= end: # 2. call is_prime function, to determine if it is prime
if is_prime(num): # 3. if you find at least one prime, has_prime should
print(num) # return True, False otherwise
found_prime = True pass
# As soon as you find the first prime, your work
# here is done, hence the break out of the loop!
break
num += 1
return found_prime
``` ```
%% Cell type:code id:0f7bd5ca tags: %% Cell type:code id:5cde0776 tags:
``` python ``` python
has_prime(14, 16) has_prime(14, 16)
``` ```
%% Output %% Cell type:code id:3a5be934 tags:
False
%% Cell type:code id:4fd676f3 tags:
``` python ``` python
has_prime(1000000, 1001000) has_prime(1000000, 1001000)
``` ```
%% Output %% Cell type:markdown id:12c14f3b tags:
1000003
True
%% Cell type:markdown id:dfc74fed tags:
## `continue` example ## `continue` example
- `continue` enables to move on to the next iteration of the while loop - `continue` enables to move on to the next iteration of the while loop
- typically used with a conditional; that is you continue when condition evaluates to `True` - typically used with a conditional; that is you continue when condition evaluates to `True`
%% Cell type:code id:e90b47b5 tags: %% Cell type:code id:ef8d6e0b tags:
``` python ``` python
total = 0 # sum # TODO: write an infinite loop using while
count = 0
while True: # TODO: get user input for age
#Handle "q" input for quitting
age = input("Enter an age [0-100]: ")
if age == "q":
break
age = float(age) # Goal: to compute running average
# It is easy to keep track of total and number of user
# inputs to compute running average
if age < 0 or age > 100: # TODO: discuss what is acceptable range for age
print("Bad input!") # What is the guinness world record for oldest person?
continue
total += age # TODO: discuss where you will initialize variables to keep track
count += 1 # of total and number of user inputs so far and then type the
# computation lines to compute updated total and running average
print("Average age of user so far is: ", total / count) # Now, try entering input as a large number outside of your
``` # acceptable age range. What happens to your average?
# TODO: handle this by writing a conditional and use continue,
# when user enters invalid age
%% Output # Finally, how do we terminate the infinite while loop
# Let's accept "q" as user input for termination
Enter an age [0-100]: 10 # TODO: handle that using another conditional
Average age of user so far is: 10.0 # Think carefully about where this conditional needs to be in
Enter an age [0-100]: 20 # terms of control flow
Average age of user so far is: 15.0 ```
Enter an age [0-100]: 102
Bad input!
Enter an age [0-100]: q
%% Cell type:markdown id:8b037e4f tags: %% Cell type:markdown id:944cc596 tags:
### After lecture ### After lecture
%% Cell type:markdown id:bf87a5ac tags: %% Cell type:markdown id:0820ba66 tags:
How many times is the *while loop condition line* executed? How many times is the *while loop condition line* executed?
%% Cell type:code id:cb6bb684 tags: %% Cell type:code id:c3c14b7b tags:
``` python ``` python
n = 7 n = 7
while n >= 5: while n >= 5:
print(n) print(n)
n -= 1 n -= 1
# Answer is 4. # Answer is 4.
# Loop condition line always gets executed number of # Loop condition line always gets executed number of
# iterations + 1 times. # iterations + 1 times.
``` ```
%% Cell type:markdown id:4def9307 tags: %% Cell type:markdown id:7cf19523 tags:
Refactor the below function. Refactor the below function.
%% Cell type:code id:9421ad49 tags: %% Cell type:code id:a313a32f tags:
``` python ``` python
def is_between(a, b, c): def is_between(a, b, c):
"""Return True if b is between a and c (exclusive), """Return True if b is between a and c (exclusive),
False otherwise""" False otherwise"""
if a < c: if a < c:
if a < b and b < c: if a < b and b < c:
return True return True
else: else:
return False return False
elif c <= a: elif c <= a:
if c < b and b < a: if c < b and b < a:
return True return True
else: else:
return False return False
else: else:
return False return False
print(is_between(1, 3, 2)) # False print(is_between(1, 3, 2)) # False
print(is_between(5, 11, 20)) # True print(is_between(5, 11, 20)) # True
print(is_between(20, 3, 5)) # False print(is_between(20, 3, 5)) # False
print(is_between(50, 11, 9)) # True print(is_between(50, 11, 9)) # True
print(is_between(4, 4, 4)) # False print(is_between(4, 4, 4)) # False
``` ```
%% Output %% Cell type:code id:7fd82ae9 tags:
False
True
False
True
False
%% Cell type:code id:21951d05 tags:
``` python ``` python
def is_between_v2(a, b, c): def is_between_v2(a, b, c):
return a < b < c or c < b < a return ???
print(is_between_v2(1, 3, 2)) # False print(is_between_v2(1, 3, 2)) # False
print(is_between_v2(5, 11, 20)) # True print(is_between_v2(5, 11, 20)) # True
print(is_between_v2(20, 3, 5)) # False print(is_between_v2(20, 3, 5)) # False
print(is_between_v2(50, 11, 9)) # True print(is_between_v2(50, 11, 9)) # True
print(is_between_v2(4, 4, 4)) # False print(is_between_v2(4, 4, 4)) # False
``` ```
%% Output %% Cell type:markdown id:ca9037f7 tags:
False
True
False
True
False
%% Cell type:markdown id:0f71dc12 tags:
Trace the output without using Python interpreter Trace the output without using Python interpreter
%% Cell type:code id:b942d01f tags: %% Cell type:code id:ec8b1b32 tags:
``` python ``` python
x = 1 x = 1
while x < 5: while x < 5:
y = 1 y = 1
while y < 10: while y < 10:
print (x * y, "\t", end="") print (x * y, "\t", end="")
y += 1 y += 1
print() print()
x += 1 x += 1
``` ```
%% Cell type:code id:7743e03b tags: %% Cell type:code id:74060bc4 tags:
``` python ``` python
width = 9 width = 9
height = 4 height = 4
symbol = '#' symbol = '#'
row = 0 row = 0
while row < height: while row < height:
col = 0 col = 0
if row % 2 == 1: if row % 2 == 1:
print(" ", end="") print(" ", end="")
while col < width: while col < width:
print(symbol + ' ', end="") print(symbol + ' ', end="")
col += 1 col += 1
# displays just a newline # displays just a newline
print() # recall default value for end parameter is "\n" print() # recall default value for end parameter is "\n"
row += 1 row += 1
``` ```
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