3-Python-Basics-Part-2.pdf

Python Basics Lesson 2 Outline: 1. Input/Print Function 2. Output Formatting 3. Import Function 4. String Operations 5. List Methods 6. Slicing 7. Operators and Basic Mathematical Function 8. Built-in Functions Input/Output (I/O) The purpose of a program is to get an i...

Python Basics Lesson 2 Outline: 1. Input/Print Function 2. Output Formatting 3. Import Function 4. String Operations 5. List Methods 6. Slicing 7. Operators and Basic Mathematical Function 8. Built-in Functions Input/Output (I/O) The purpose of a program is to get an input, process it, optionally store it, and display the results afterwards. Python has functions that allow the programmer to get user input and display messages. Input Function The input() function takes input from the user and returns it. To store a value, it can be assigned to a variable using the syntax below. = input() Example: value = input("Enter a value: ") Input Function Example: number = input(“Enter a number: “) Enter a number: 10 10 Note that the inputted value 10 is a string. You need to convert this into a number. Use int() or float() functions. Input Function number = int(input("Enter a number: ")) the value must be compatible when in comes of conversion Print Function In order to display something, the print() function can be used. Example: value = input("Enter a value: ") print(value) Output Formatting Sometimes we would like to format our output to make it look attractive. This can be done by using the str.format() method. This method is visible to any string object. Output Formatting For example: x = 5; y = 10 print(“The value of x is {} and y is {}”.format(x,y)) Output: The value of x is 5 and y is 10. The curly braces {} are used as placeholders. Output Formatting Another example: print(‘ I love {0} and {1} ‘.format(‘bread’, ’butter’)) print( ‘ I love {1} and {0}’.format(‘bread’, ’butter’)) Output: I love bread and butter I love butter and bread The curly braces {} are used as placeholders. We can specify the order in which they are printed by using numbers (tuple index). Output Formatting We can also use keyword arguments to format the string. print(‘Hello {name}, {adj}’.format(adj = ‘Handsome’, name = ‘John’)) Result: Hello John, Handsome Output Formatting Another way to format: Example: x=5 y = 10 print(f“The value of x is {x} and y is {y}”) Output: The value of x is 5 and y is 10 Output Formatting Example: x=5 y = 10 total = x + y print(f"The sum of the two integer is {total}") Output: The sum of the two integer is 15 Output Formatting How input() works in Python Example 1: #Get input from user inputString = input(“ ”) print('The inputted String is:', inputString) Or: print(f“The inputted String is: {inputString}”) How input() works in Python Example 2: #Taking two integers from users and adding them. #Taking num1 from user as int num1 = input('Please Enter First Number:') num1 = int(num1) #Taking number 2 from user as int num2 = input('Please Enter Second Number:') num2 = int(num2) addition = num1 + num2 print(addition) How input() works in Python Example 2: #Taking two integers from users and adding them. #Taking num1 from user as int num1 = int(input('Please Enter First Number:')) #Taking number 2 from user as int num2 = int(input('Please Enter Second Number:')) addition = num1 + num2 print(addition) How input() works in Python Example 3: #Taking two integers from users and adding them. #Taking num1 from user as float num1 = float(input('Please Enter First Number:')) #Taking number 2 from user as float num2 = float(input('Please Enter Second Number:’)) addition = num1 + num2 #to round off float, use round() Function print(round(addition,2)) Import in Python Definitions inside a module can be imported to another module or the interactive interpreter in Python. We use the import keyword to do this. Example: import math print(math.pi) Import in Python import math pi = math.pi print(f"The value of pi is {pi}.") result = math.factorial(5) print(f"5 factorial: {result}") Import in Python import math pi = math.pi print("The value of pi is", pi) result = math.factorial(5) print("5 factorial: ", result) Import in Python We can also import some specific attributes and functions only, using the from keyword. Example: from math import pi pi Import in Python Example: from statistics import mean, median numbers = [1, 2, 3, 4, 5] average = mean(numbers) middle = median(numbers) print(f"The mean is: {average}") print(f"The median is: {middle}") Import in Python Math Module: https://docs.python.org/3/library/math.html String Operations String Operations NOTE: Applicable on strings only. String Operations NOTE: Applicable on strings only. String Operations NOTE: Applicable on strings only. String Operations the strip() method is a string method that returns a copy of the string with leading and trailing whitespace removed. String Operations the upper() method is a string method that returns a copy of the string with all characters converted to uppercase. String Operations the lower() method is a string method that returns a copy of the string with all characters converted to lowercase. String Operations the capitalize() method is a string method that returns a copy of the string with the first character converted to uppercase and all other characters converted to lowercase. String Operations the title() method is a string method that returns a copy of the string with the first character of each word capitalized and the remaining characters in lowercase. String Operations String Operations List Methods List can be modified by adding or removing a value. Other methods can also be applied to further manipulate its contents. List Methods inventory = [] # create a list # Add a new item inventory.append("screw") # insert a new item at a specific index inventory.insert(0, "hammer") List Methods inventory = [“hammer", “screw"] # remove at specific index inventory.pop(1) # remove the first occurrence inventory.remove(“hammer") List Methods inventory = [“hammer", “screw”] # count total occurrences count = inventory.count("hammer") print(f"Occurrence: {count}") # get index of first occurence index = inventory.index("screw") print(f"Index: {index}") # get the total items in the list; using len() function print(len(inventory)) List Methods inventory = [“hammer", “screw”] # change value on specific index inventory = "screw driver" # access value on specific index print(inventory) List Methods inventory = [“hammer", “screw driver”] more_items = ["pliers", "tie wire"] # extend list with more items inventory.extend(more_items) # clear all contents inventory.clear() Slicing What is Slicing? A way to get values in an ordered sequence. NOTE: Applicable on Strings, Lists, and Tuples only Slicing Slicing Operators and Basic Mathematical Function What are operators in python? Operators are special symbols in Python that carry out arithmetic or logical computation. The value that the operator operates on is called the operand. Example: a=2+3 Output: 5 Arithmetic operators Arithmetic operators are used to perform mathematical operations like addition, subtraction, multiplication, etc. Arithmetic operators Arithmetic operators Note: we can also use this: Example x = 15 y = 4 a = x + y print(f"x + y = {a}") print('x + y =',x+y) # Output: x + y = 19 print('x - y =',x-y) # Output: x - y = 11 print('x * y =',x*y) # Output: x * y = 60 Arithmetic operators Example x = 15 y = 4 print('x / y =',x/y) # Output: x / y = 3.75 print('x // y =',x//y) # Output: x // y = 3 print('x ** y =',x**y) # Output: x ** y = 50625 Arithmetic operators Increment age = 5 age += 1 # increment print(age) Output: 6 Comparison operators Comparison operators are used to compare values. It returns either True or False according to the condition. Comparison operators Comparison operators Note: we can also use this: Example x = 10 y = 12 a = x > y print(f"x > y = {a}") # Output: x > y is False print('x > y is',x>y) # Output: x < y is True print('x < y is',x= y is False print('x >= y is',x>=y) # Output: x