Python Virtual Training For Arcesium - Module I - Day 4

Sep 13-17, 2021 Vikrant Patil

These notes are available online at https://notes.pipal.in/2021/arcesium_finop_batch1/module1-day4.html

© Pipal Academy LLP

Day 1 | Day 2 | Day 3 | Day 4 | Day 5

We will be using jupyter hub from https://lab.pipal.in for this training.

login to hub and create a notebook with name module1-day4

• Use max to find longest list from list of list.

items = [[1, 2, 3, 4],
         [1, 1, 1],
         [1, 2, 3, 4, 5, 6, 7],
         [2]
         [1, 2, 3, 4, 5]]

• A dictionary has names of courses and value for each course is list of books needed for that course. Use min function to find out a course with minimum books needed.

courses = {
    "practical python": ["Python practice book", "Python for finance", "Python cookbook"],
    "elegant programming": ["SICP", "Python programming", "Art of Programming"],
    "python primer": ["Python practice book", "Python from scratch"],
    "extreme programming": ["Async Python", "Web and Python", "Optimizing python code", "Advanced Python"]
}

def sumof(x, y, func):
    return func(x) + func(y)

items = [[1, 2, 3, 4],
         [1, 1, 1],
         [1, 2, 3, 4, 5, 6, 7],
         [2],
         [1, 2, 3, 4, 5]]

len("hello")

5

len([1, 2, 3, 4])

4

max(items, key=len)

[1, 2, 3, 4, 5, 6, 7]

courses = {
    "practical python": ["Python practice book", "Python for finance", "Python cookbook"],
    "elegant programming": ["SICP", "Python programming", "Art of Programming"],
    "python primer": ["Python practice book", "Python from scratch"],
    "extreme programming": ["Async Python", "Web and Python", "Optimizing python code", "Advanced Python"]
}

def number_of_books(coursename):
    num_books = len(courses[coursename])
    print("Coursename:", coursename, "num_books", num_books)
    return num_books

min(courses, key=number_of_books)

Coursename: practical python num_books 3
Coursename: elegant programming num_books 3
Coursename: python primer num_books 2
Coursename: extreme programming num_books 4

'python primer'

courses.keys()

dict_keys(['practical python', 'elegant programming', 'python primer', 'extreme programming'])

courses.values()

dict_values([['Python practice book', 'Python for finance', 'Python cookbook'], ['SICP', 'Python programming', 'Art of Programming'], ['Python practice book', 'Python from scratch'], ['Async Python', 'Web and Python', 'Optimizing python code', 'Advanced Python']])

courses.items()

dict_items([('practical python', ['Python practice book', 'Python for finance', 'Python cookbook']), ('elegant programming', ['SICP', 'Python programming', 'Art of Programming']), ('python primer', ['Python practice book', 'Python from scratch']), ('extreme programming', ['Async Python', 'Web and Python', 'Optimizing python code', 'Advanced Python'])])

len(courses)

4

courses['python primer']

['Python practice book', 'Python from scratch']

len(courses['python primer'])

2

def longest_book_name(coursename):
    books = courses[coursename]
    return len(max(books, key=len))

min(courses, key=longest_book_name)

'elegant programming'

courses

{'practical python': ['Python practice book',
  'Python for finance',
  'Python cookbook'],
 'elegant programming': ['SICP', 'Python programming', 'Art of Programming'],
 'python primer': ['Python practice book', 'Python from scratch'],
 'extreme programming': ['Async Python',
  'Web and Python',
  'Optimizing python code',
  'Advanced Python']}

def get_books(key_value):
    print(key_value)
    return len(key_value[1])

max(courses.items(), key=get_books)

('practical python', ['Python practice book', 'Python for finance', 'Python cookbook'])
('elegant programming', ['SICP', 'Python programming', 'Art of Programming'])
('python primer', ['Python practice book', 'Python from scratch'])
('extreme programming', ['Async Python', 'Web and Python', 'Optimizing python code', 'Advanced Python'])

('extreme programming',
 ['Async Python',
  'Web and Python',
  'Optimizing python code',
  'Advanced Python'])

min(courses.items(), key=get_books)

('practical python', ['Python practice book', 'Python for finance', 'Python cookbook'])
('elegant programming', ['SICP', 'Python programming', 'Art of Programming'])
('python primer', ['Python practice book', 'Python from scratch'])
('extreme programming', ['Async Python', 'Web and Python', 'Optimizing python code', 'Advanced Python'])

('python primer', ['Python practice book', 'Python from scratch'])

t = ('python primer', ['Python practice book', 'Python from scratch'])

t[0]

'python primer'

t[1]

['Python practice book', 'Python from scratch']

t[1][0]

'Python practice book'

Functions that return a function

def make_adder(x):
    
    def adder(y):
        return x+y
    
    return adder # it is returning a function

adder5 = make_adder(5) # x is given here as parameter

adder5

<function __main__.make_adder.<locals>.adder(y)>

adder5(7)

12

adder5(9)

14

f = lambda x,y: x+y

f(3,4)

7

sqr = lambda x: x*x

sqr(5)

25

def foo():
    print("hello")

def make_adder(x):
    
    def adder(y):
        return x+y
    
    return adder(7) # this is not returning a function

make_adder(5)

12

make_adder(8)

15

def make_logger(type_):
    
    def print_message(message):
        return print(type_.upper() + ":", message)
    
    return print_message

warning = make_logger("warn") ##
info = make_logger("info")
error = make_logger("error")

warning("Your input contains floats! I expect integers")

WARN: Your input contains floats! I expect integers

info("Your input look of, I am processing")

INFO: Your input look of, I am processing

error("Something went wrong, division by zero!")

ERROR: Something went wrong, division by zero!

Programming constructs

Conditions

True

True

False

False

"hello".endswith("o")

True

"hel" in "Hello"

False

"Hel" in "Hello"

True

1 in [1, 2, 3, 4]

True

courses

{'practical python': ['Python practice book',
  'Python for finance',
  'Python cookbook'],
 'elegant programming': ['SICP', 'Python programming', 'Art of Programming'],
 'python primer': ['Python practice book', 'Python from scratch'],
 'extreme programming': ['Async Python',
  'Web and Python',
  'Optimizing python code',
  'Advanced Python']}

"python primer" in courses # it will check in keys only

True

x = 10
y = 15

x == y

False

x == 5

False

x == 10

True

1 not in [2, 3, 4, 5, 6]

True

1 not in [1, 2, 3, 4]

False

x, y = 2, 4

x

2

y

4

x, y = [4, 5]

x

4

y

5

x, y = (5, 6)

x

5

y

6

x > y

False

x >= y

False

x < y

True

x <= y

True

x != y

True

print(x, y)

5 6

cond = True
if cond:
    print("hello")

hello

if "hel" in "cell":
    x = 10
    y = 20
    z = x+y
    print("hell!") 
elif "cel" in "hell":
    print("cell")
elif "del" in "bell":
    print("dell")
else:
    print("oops!")

oops!

[1, 2] in [1, 2, 3, 4]

False

[1, 2] in [[1,2],[2,3],[3,4]]

True

While loop

i = 0 
while i < 5:
    print(i)
    i = i + 1
    
    

0
1
2
3
4

words = "This is some sentence for testing while loop".split()
print(words)

i = 0
while i<len(words):#possibility of having wrong condition..might result in infite loop
    print(words[i]) # if indexing goes wrong possibility of going out of index
    i = i +1

['This', 'is', 'some', 'sentence', 'for', 'testing', 'while', 'loop']
This
is
some
sentence
for
testing
while
loop

def print_fib(n):
    """print fibonacci numbers lees than n
    """
    curr, prev = 1, 1
    
    while prev<n:
        print(prev, end=",")#after every print put a comma insted new line
        curr , prev = prev+curr, curr
        

print_fib(1000)

1,1,2,3,5,8,13,21,34,55,89,144,233,377,610,987,

for loops

words

['This', 'is', 'some', 'sentence', 'for', 'testing', 'while', 'loop']

for word in words:
    print(word)

This
is
some
sentence
for
testing
while
loop

for c in "hello":
    print(c)

h
e
l
l
o

for coursename in courses: #loop over keys
    print(coursename)

practical python
elegant programming
python primer
extreme programming

for books in courses.values():
    print (books)

['Python practice book', 'Python for finance', 'Python cookbook']
['SICP', 'Python programming', 'Art of Programming']
['Python practice book', 'Python from scratch']
['Async Python', 'Web and Python', 'Optimizing python code', 'Advanced Python']

for key, value in courses.items():
    print(key, value)

practical python ['Python practice book', 'Python for finance', 'Python cookbook']
elegant programming ['SICP', 'Python programming', 'Art of Programming']
python primer ['Python practice book', 'Python from scratch']
extreme programming ['Async Python', 'Web and Python', 'Optimizing python code', 'Advanced Python']

def mysum(numbers):
    s = 0 
    for n in numbers:
        s = s + n
    return s

mysum([1,2, 3, 4, 5, 6, 8])

29

list(range(10))

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

list(range(5, 100, 5))

[5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95]

for i in range(5):
    print(i)

0
1
2
3
4

mysum((1, 2, 3, 4, 5))

15

problems

• Write a function product which finds product of all elements from a list/coolection.

  >>> product([3, 2, 4])
  24

• Write a function factorial which computes factorial of a number.

  >>> factorial(5)
  120

• Write a function findlens which will find length of every word from a list of words

  >>> findlens(["one", "two", "three"])
  [3, 3, 5]

• Write a function which finds words of given length from given list of words.

  >>> words = ["one", "two", "three", "four", "five", "six"]
  >>> find_words_of_len(words, 3)
  ["one", "two", "six"]

bonus

• Write a function unique which will remove duplicates from a list:

  >>> unique([1, 1, 1, 2, 2, 3, , 4, 4, 5])
  [1, 2, 3, 4, 5]

if x == y:
    print("equal")
else:
    print("unequal")

unequal

del i

def func():
    #i = 0
    while i < 5:
        i = i +1
        print(i)
    

func()

---------------------------------------------------------------------------
UnboundLocalError                         Traceback (most recent call last)
<ipython-input-114-bd1982955a12> in <module>
----> 1 func()

<ipython-input-113-86ce4d620c3a> in func()
      1 def func():
      2     #i = 0
----> 3     while i < 5:
      4         i = i +1
      5         print(i)

UnboundLocalError: local variable 'i' referenced before assignment

#product(1, 2, 3) # three argument!
#product([1, 2, 3]) # signle argment, which is a list

---------------------------------------------------------------------------
UnboundLocalError                         Traceback (most recent call last)
<ipython-input-116-bd1982955a12> in <module>
----> 1 func()

<ipython-input-113-86ce4d620c3a> in func()
      1 def func():
      2     #i = 0
----> 3     while i < 5:
      4         i = i +1
      5         print(i)

UnboundLocalError: local variable 'i' referenced before assignment

mysum([1, 2, 3, 4])

10

mysum([1, 2, 3, 4])

10

for i in 4:
    print(i)
    

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-120-d5ac0dd5fd2d> in <module>
----> 1 for i in 4:
      2     print(i)
      3 

TypeError: 'int' object is not iterable

for i in range(4):
    print(i)

0
1
2
3

for i in range(1, 5):
    print(i)

1
2
3
4

### n in num

#item in collection (list, tuple, string, dictionary)

4 in 54

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-125-511254e4adcd> in <module>
----> 1 4 in 54

TypeError: argument of type 'int' is not iterable

"4" in "54"

True

4 in [4, 5, 54]

True

def factorial(num):
    mult = 1 
    n = 1
    
    while n <= num:
        mult = mult*n
        n = n+1
        
    return mult
        

factorial(5)

120

def findlens(words):
    lens = [] # empty list
    
    for word in words:
        length = len(word)
        lens.append(length)
        
    return lens

findlens(words)

[4, 2, 4, 8, 3, 7, 5, 4]

words

['This', 'is', 'some', 'sentence', 'for', 'testing', 'while', 'loop']

def make_upper(words):
    upper_words = []
    
    for word in words:
        upper = word.upper()
        upper_words.append(upper)
        
    return upper_words

make_upper(words)

['THIS', 'IS', 'SOME', 'SENTENCE', 'FOR', 'TESTING', 'WHILE', 'LOOP']

def make_squares(numbers):
    sqrs = []
    
    for num in numbers:
        s = num**2
        sqrs.append(s) # adding next value
        
    return sqrs
        

make_squares([2, 3, 4, 5, 2, 3, 5])

[4, 9, 16, 25, 4, 9, 25]

",".join(words)

'This,is,some,sentence,for,testing,while,loop'

":".join(words)

'This:is:some:sentence:for:testing:while:loop'

" ".join(words)

'This is some sentence for testing while loop'

def func_with_two_values(x):
    return x, x+5
    

func_with_two_values(7)

(7, 12)

a, b = func_with_two_values (7)

def product(numbers):
    p = 1
    
    for num in numbers:
        p = p * num
        
    return p

product([2, 3, 4, 5])

120

product([1, 6, 7])

42

def factorial(n):
    return product(range(1, n+1))

factorial(5)

120

factorial(-1)

1

factorial(0)

1

list(range(1, 5))

[1, 2, 3, 4]

list(range(5))

[0, 1, 2, 3, 4]

list(range(5, 50, 5)) # start, end, step

[5, 10, 15, 20, 25, 30, 35, 40, 45]

def find_words_of_len(words, l):
    """find all words of length l from given words
    """
    newwords = []
    
    for word in words:
        length = len(word)
        if length == l:
            newwords.append(word)
            
    return newwords

find_words_of_len(words, 2)

['is']

find_words_of_len(words, 4)

['This', 'some', 'loop']

def unique(items):
    my_collection = []
    
    for item in items:
        if item not in my_collection:
            my_collection.append(item)
            
    return my_collection
            

[1, 1, 2, 3, 4, 5, 5, 6, 6, 6]

unique items

[1, 2, 3, 4, 5, 6]

unique([1, 1, 1, 2, 3, 2, 4, 5,5, 5, 5, 6, 2, 3, 1, 6, 6])

[1, 2, 3, 4, 5, 6]

tips for looping

• Whenever you are working with a collection , use for loop
• if there no collection as such in the problem , does that convert finally into a collection? if yes use for loop
• by making use of range function you can mostly make use for loop!
• no none of above, then use while loop

for i in range(5,20, 3):
    print(i)

5
8
11
14
17

i = 5
while i < 20:#possible error
    print(i)
    i = i + 3 #possible error

5
8
11
14
17