Python Basics

#### EXAMPLE OF CREATING A VARIABLE #### # You use # to add comment, it won’t run or affect the code # You use = to assign a value to the name of the variable. # Each code starts on the new line. No semicolon or {} var_name = 1 str_var2 = 'Hundred'

int_var = 10 float_var = 12.8 type(int_var)

type(float_var)

# Numeric Operations # Addition 1 + 100

# Multiplication 1 * 100

# Division 1 / 100

# Modular (%) # This is the remainder or a value remaining after dividing two numbers # 100 / 1 = 100, remainder is 0 100 % 1

1 % 100

10 % 2

# Powers # 1 power any number is 1 always 1 ** 100

2 ** 2

# We use print() to display the results of the operations or a variable print(1 + 100)

str_var = 'One' str_var2 = 'Hundred'

str_var + str_var2

str_var + ' ' + 'and' + ' '+ str_var2+ '.'

## We can use print() to display a string print(" This is a string")

sentence = 'This is a String'

# Case capitalization # It return the string with first letter capitalized and the rest being lower cases. sentence.capitalize()

# Given a string, convert it into title (each word is capitalized) another_sentence = 'this is a string to be titled' another_sentence.title()

# Converting the string to upper case sentence.upper()

# Converting the string to upper case sentence.lower()

# Splitting the string sentence.split()

# Example of list #### week_days = ['Mon', 'Tue', 'Wed', 'Thur','Fri'] even_numbers = [2,4,6,8,10] mixed_list = ['Mon', 1, 'Tue', 2, 'Wed', 3]

#### Accessing the elements of the list week_days[0]

print(even_numbers[2])

print(even_numbers[-1])

# Slicing the list week_days = ['Mon', 'Tue', 'Wed', 'Thur','Fri'] week_days[0:2]

week_days[-4:] # -1 starts at 'Fri', -2 to `Thur'..... -4 to 'Tue'

# Updating the value of the list even_numbers = [2,4,6,8,10] # Change the value at index or position 3 (position starts at 0) to 12 even_numbers[3] = 12 even_numbers

even_numbers[2:4] = [16,20] even_numbers

# Adding the new elements in list odd_numbers = [1,3,5,7,9] odd_numbers = [1,3,5,7,9] odd_numbers.append(11) odd_numbers.append(13) odd_numbers

## Concatenating two lists a = [1,2,3] b = [4,5,6] c = a + b c

# Nesting a list in other list nested_list = [1,2,3, ['a', 'b', 'c']] nested_list[3]

# Calculating the length of the list odd_numbers = [1,3,5,7,9] len(odd_numbers)

# Sorting a list even_numbers = [2,14,16,12,20,8,10] even_numbers.sort() even_numbers

# Reversing a string even_numbers.reverse() even_numbers

# Adding other elements to a list even_numbers = [2,14,16,12,20,8,10] even_numbers.append(40) even_numbers

# Removing the first element of a list even_numbers.remove(2) even_numbers

## Return the element of the list at index x even_numbers = [2,14,16,12,20,8,10] ## Return the item at the 1st index even_numbers.pop(1)

# pop() without index specified will return the last element of the list even_numbers = [2,14,16,12,20,8,10] even_numbers.pop()

# Count a number of times an element appear in a list even_numbers = [2,2,4,6,8] even_numbers.count(2)

# Example of Dictionary # Countries codes: https://countrycode.org countries_code = { "United States": 1, "India": 91, "Germany": 49, "China": 86, "Rwanda":250 }

countries_code

countries_code.items()

countries_code.keys()

countries_code.values()

countries_code['India']

countries_code['Rwanda']

# Adding new country and code countries_code['Cuba'] = 53 countries_code

tup = (1,4,5,6,7,8)

# Indexing tup[4]

## Tuples are not changeable. Running below code will cause an error # tup[2] = 10

# You can not also add other values to the tuple. This will be error #tup.append(12)

set_1 = {1,2,3,4,5,6,7,8} set_1

set_2 = {1,1,2,3,5,3,2,2,4,5,7,8,8,5} set_2

# List Vs Set odd_numbers = [1,1,3,7,9,3,5,7,9,9] print("List:{}".format(odd_numbers)) print("#####") set_odd_numbers = {1,1,3,7,9,3,5,7,9,9} print("Set:{}".format(set_odd_numbers))

## Greater than 100 > 1

## Equal to 100 == 1

## Less than 100 < 1

## Greater or equal to 100 >= 1

## Less or equal to 100 <= 1

'Intro to Python' == 'intro to python'

'Intro to Python' == 'Intro to Python'

100 == 100 and 100 == 100

100 <= 10 and 100 == 100

100 == 10 or 100 == 100

100 == 10 or 100 == 10

not 1 == 2

not 1 == 1

if 100 < 2: print("As expected, no thing will be displayed")

if 100 > 2: print("As expected, no thing will be displayed")

if 100 < 2: print("As expected, no thing will be displayed") else: print('Printed')

# Let's assign a number to a variable name 'jean_age' and 'yannick_age' john_age = 30 luck_age = 20 if john_age > luck_age: print("John is older than Luck") else: print(" John is younger than Luck")

# Let's use multiple conditions john_age = 30 luck_age = 20 yan_age = 30 if john_age < luck_age: print("John is older than Luck") elif yan_age == luck_age: print(" Yan's Age is same as Luck") elif luck_age > john_age: print("Luck is older than John") else: print("John's age is same as Yan")

# Example 1: Return 'Even' if below num is 'Even' and `Odd` if not. num = 45 'Even' if num % 2 == 0 else 'Odd'

# Example 2: Return True if a given element is in a list and False if not nums = [1,2,3,4,5,6] True if 3 in nums else False

even_nums = [2,4,6,8,10] for num in even_nums: print(num)

week_days = ['Mon', 'Tue', 'Wed', 'Thur','Fri'] for day in week_days: print(day)

sentence = "It's been a long time learning Python. I am revisiting the basics!!" for letter in sentence: print(letter)

sentence = "It's been a long time learning Python. I am revisiting the basics!!" # split is a string method to split the words making the string for letter in sentence.split(): print(letter)

# For loop in dictionary countries_code = { "United States": 1, "India": 91, "Germany": 49, "China": 86, "Rwanda":250 } for country in countries_code: print(country)

for code in countries_code.values(): print(code)

for number in range(10): print(number)

for number in range(10, 20): print(number)

letters = [] for letter in 'MachineLearning': letters.append(letter) letters

letters = [letter for letter in 'MachineLearning'] letters

a = 10 while a < 20: print('a is: {}'.format(a)) a = a + 1

# Function to add two numbers and return a sum def add_nums(a,b): """ Function to add two numbers given as inputs It will return a sum of these two numbers """ sum = a+b return sum

add_nums(2,4)

add_nums(4,5)

# Displaying the doc string noted early print(add_nums.__doc__)

def activity(name_1, name_2): print("{} and {} are playing basketball!".format(name_1, name_2))

activity("Chris", "Francois")

activity("Kennedy", "Kleber")

## Sum of two numbers def add_nums(a,b): sum = a+b return sum add_nums(1,3)

sum_of_two_nums = lambda c,d: c + d sum_of_two_nums(4,5)

# using len() to count the length of the string message = 'Do not give up!' len(message)

odd_numbers = [1,3,5,7] len(odd_numbers)

# Using max() to find the maximum number in a list odd_numbers = [1,3,5,7] max(odd_numbers)

# Using min() to find the minimum number in a list min(odd_numbers)

# Sorting the list with sorted() odd_numbers = [9,7,3,5,11,13,15,1] sorted(odd_numbers)

def cubic(number): return number ** 3

num_list = [0,1,2,3,4]

# Applying `map` to the num_list to just return the list where each element is cubed...(xxx3) list(map(cubic, num_list))

def odd_check(number): return number % 2 != 0 # != is not equal to operation

num_list = [1,2,4,5,6,7,8,9,10,11] list(filter(odd_check, num_list))

# Given a list of numbers, can you make a new list of even numbers from the list nums? # Even numbers are numbers divisible by 2, and they give the remainder of 0 nums = range(1,20) even_nums = [] # A traditional way to do it is: for num in nums: if num % 2 == 0: even_nums.append(num) print(even_nums)

even_nums = [num for num in nums if num % 2 == 0] print(even_nums)

days = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday'] day_T = [] # Make a list of days that start with `T` for day in days: if day[0] == 'T': day_T.append(day) print(day_T)

day_T = [day for day in days if day[0] == 'T'] print(day_T)

seasons = ['Spring', 'Summer', 'Fall', 'Winter'] list(enumerate(seasons))

list(enumerate(seasons, start=1))

class_names = ['Rock', 'Paper', 'Scissor'] for index, class_name in enumerate(class_names, start=0): print(index,'-',class_name)

name = ['Jessy', 'Joe', 'Jeannette'] role = ['ML Engineer', 'Web Developer', 'Data Engineer'] zipped_name_role = zip(name, role) zipped_name_role

list(zipped_name_role)