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Commit e40b7730 authored by msyamkumar's avatar msyamkumar
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Lec 11 notebooks

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f22/meena_lec_notes/lec-11/lec_11_Iteration_2.ipynb
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View file @ e40b7730
%% Cell type:markdown id:1fd5544f tags:
# Iteration 2
## Readings:
- Chapter 2 of Sweigart book
- Chapter 6.4 of Python for Everybody
%% Cell type:code id:e15b9d08 tags:
``` python
import math
```
%% Cell type:markdown id:ebce36a5 tags:
## Learning Objectives
- Read and trace through Python code containing nested loops.
- Read and trace through Python code using `break` or `continue` in a `while` loop
- Determine the effect of break and continue in nested loops
%% Cell type:markdown id:8f91daea tags:
## `break` example
- `break` enables to terminate execution of a while loop
- typically used with a conditional; that is you break when condition evaluates to `True`
%% Cell type:code id:5ec2099a tags:
``` python
def is_prime(num):
""" returns True if x is prime, false otherwise.
Assumes x is positive"""
# try all divisors from 2 to sqrt(num) to check if num is prime
divisor = 2
while divisor <= math.sqrt(num):
# check if num is divisible by divisor
if num % divisor == 0:
return False
divisor += 1
return True
```
%% Cell type:code id:18f5a22c tags:
``` python
print(is_prime(1))
print(is_prime(2))
print(is_prime(3))
print(is_prime(7))
print(is_prime(16))
print(is_prime(23))
print(is_prime(1000000))
```
%% Output
True
True
True
True
False
True
False
%% Cell type:code id:daca8575 tags:
``` python
def has_prime(start, end):
found_prime = False
num = start
while num <= end:
if is_prime(num):
print(num)
found_prime = True
# 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:
``` python
has_prime(14, 16)
```
%% Output
False
%% Cell type:code id:4fd676f3 tags:
``` python
has_prime(1000000, 1001000)
```
%% Output
1000003
True
%% Cell type:markdown id:dfc74fed tags:
## `continue` example
- `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`
%% Cell type:code id:e90b47b5 tags:
``` python
total = 0 # sum
count = 0
while True:
#Handle "q" input for quitting
age = input("Enter an age [0-100]: ")
if age == "q":
break
age = float(age)
if age < 0 or age > 100:
print("Bad input!")
continue
total += age
count += 1
print("Average age of user so far is: ", total / count)
```
%% Output
Enter an age [0-100]: 10
Average age of user so far is: 10.0
Enter an age [0-100]: 20
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:
### After lecture
%% Cell type:markdown id:bf87a5ac tags:
How many times is the *while loop condition line* executed?
%% Cell type:code id:cb6bb684 tags:
``` python
n = 7
while n >= 5:
print(n)
n -= 1
# Answer is 4.
# Loop condition line always gets executed number of
# iterations + 1 times.
```
%% Cell type:markdown id:4def9307 tags:
Refactor the below function.
%% Cell type:code id:9421ad49 tags:
``` python
def is_between(a, b, c):
"""Return True if b is between a and c (exclusive),
False otherwise"""
if a < c:
if a < b and b < c:
return True
else:
return False
elif c <= a:
if c < b and b < a:
return True
else:
return False
else:
return False
print(is_between(1, 3, 2)) # False
print(is_between(5, 11, 20)) # True
print(is_between(20, 3, 5)) # False
print(is_between(50, 11, 9)) # True
print(is_between(4, 4, 4)) # False
```
%% Output
False
True
False
True
False
%% Cell type:code id:21951d05 tags:
``` python
def is_between_v2(a, b, c):
return a < b < c or c < b < a
print(is_between_v2(1, 3, 2)) # False
print(is_between_v2(5, 11, 20)) # True
print(is_between_v2(20, 3, 5)) # False
print(is_between_v2(50, 11, 9)) # True
print(is_between_v2(4, 4, 4)) # False
```
%% Output
False
True
False
True
False
%% Cell type:markdown id:0f71dc12 tags:
Trace the output without using Python interpreter
%% Cell type:code id:b942d01f tags:
``` python
x = 1
while x < 5:
y = 1
while y < 10:
print (x * y, "\t", end="")
y += 1
print()
x += 1
```
%% Cell type:code id:7743e03b tags:
``` python
width = 9
height = 4
symbol = '#'
row = 0
while row < height:
col = 0
if row % 2 == 1:
print(" ", end="")
while col < width:
print(symbol + ' ', end="")
col += 1
# displays just a newline
print() # recall default value for end parameter is "\n"
row += 1
```
......
f22/meena_lec_notes/lec-11/lec_11_Iteration_2_template.ipynb
+ 6
− 2
View file @ e40b7730
%% Cell type:markdown id:cce4a7bf tags:
# Iteration 2
## Readings:
- Chapter 2 of Sweigart book
- Chapter 6.4 of Python for Everybody
%% Cell type:code id:7693263d tags:
``` python
import math
```
%% Cell type:markdown id:0b7e0914 tags:
## Learning Objectives
- Read and trace through Python code containing nested loops.
- Read and trace through Python code using `break` or `continue` in a `while` loop
- Determine the effect of break and continue in nested loops
%% Cell type:markdown id:06b520a0 tags:
## `break` example
- `break` enables to terminate execution of a while loop
- typically used with a conditional; that is you break when condition evaluates to `True`
%% Cell type:code id:8067fa3e tags:
``` python
def is_prime(num):
""" returns True if x is prime, false otherwise.
Assumes x is positive"""
# try all divisors from 2 to sqrt(num) to check if num is prime
divisor = ???
while ???:
# check if num is divisible by divisor
if num % divisor == ???:
return ???
divisor ???
return ???
```
%% Cell type:code id:2e3d3f29 tags:
``` python
print(is_prime(1))
print(is_prime(2))
print(is_prime(3))
print(is_prime(7))
print(is_prime(16))
print(is_prime(23))
print(is_prime(1000000))
```
%% Cell type:code id:9a28c726 tags:
``` python
def has_prime(start, end):
# TODO: write a for loop using range, to:
# 1. iterate over every number from start to end
# 2. call is_prime function, to determine if it is prime
# 3. if you find at least one prime, has_prime should
# return True, False otherwise
pass
```
%% Cell type:code id:5cde0776 tags:
``` python
has_prime(14, 16)
```
%% Cell type:code id:3a5be934 tags:
``` python
has_prime(1000000, 1001000)
```
%% Cell type:markdown id:12c14f3b tags:
## `continue` example
- `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`
%% Cell type:code id:ef8d6e0b tags:
``` python
# TODO: write an infinite loop using while
# TODO: get user input for age
# Goal: to compute running average
# It is easy to keep track of total and number of user
# inputs to compute running average
# TODO: discuss what is acceptable range for age
# What is the guinness world record for oldest person?
# TODO: discuss where you will initialize variables to keep track
# of total and number of user inputs so far and then type the
# computation lines to compute updated total and running average
# 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
# Finally, how do we terminate the infinite while loop
# Let's accept "q" as user input for termination
# TODO: handle that using another conditional
# Think carefully about where this conditional needs to be in
# terms of control flow
```
%% Cell type:markdown id:944cc596 tags:
### After lecture
%% Cell type:markdown id:0820ba66 tags:
How many times is the *while loop condition line* executed?
%% Cell type:code id:c3c14b7b tags:
``` python
n = 7
while n >= 5:
print(n)
n -= 1
# Answer is 4.
# Loop condition line always gets executed number of
# iterations + 1 times.
```
%% Cell type:markdown id:7cf19523 tags:
Refactor the below function.
%% Cell type:code id:a313a32f tags:
``` python
def is_between(a, b, c):
"""Return True if b is between a and c (exclusive),
False otherwise"""
if a < c:
if a < b and b < c:
return True
else:
return False
elif c <= a:
if c < b and b < a:
return True
else:
return False
else:
return False
print(is_between(1, 3, 2)) # False
print(is_between(5, 11, 20)) # True
print(is_between(20, 3, 5)) # False
print(is_between(50, 11, 9)) # True
print(is_between(4, 4, 4)) # False
```
%% Cell type:code id:7fd82ae9 tags:
``` python
def is_between_v2(a, b, c):
return ???
print(is_between_v2(1, 3, 2)) # False
print(is_between_v2(5, 11, 20)) # True
print(is_between_v2(20, 3, 5)) # False
print(is_between_v2(50, 11, 9)) # True
print(is_between_v2(4, 4, 4)) # False
```
%% Cell type:markdown id:ca9037f7 tags:
Trace the output without using Python interpreter
%% Cell type:code id:ec8b1b32 tags:
``` python
x = 1
while x < 5:
y = 1
while y < 10:
print (x * y, "\t", end="")
y += 1
print()
x += 1
```
%% Cell type:code id:74060bc4 tags:
``` python
width = 9
height = 4
symbol = '#'
row = 0
while row < height:
col = 0
if row % 2 == 1:
print(" ", end="")
while col < width:
print(symbol + ' ', end="")
col += 1
# displays just a newline
print() # recall default value for end parameter is "\n"
row += 1
```
......
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