Python Programming Tutorial PDF

Python Programming WHAT IS PYTHON? Python is a popular programming language. It was created by Guido van Rossum, and released in 1991. It is used for: web development (server-side), software development, mathematics, system scripting. WHY PYTH...

Python Programming WHAT IS PYTHON? Python is a popular programming language. It was created by Guido van Rossum, and released in 1991. It is used for: web development (server-side), software development, mathematics, system scripting. WHY PYTHON? Python works on different platforms (Windows, Mac, Linux, Raspberry Pi, etc). Python has a simple syntax similar to the English language. Python has syntax that allows developers to write programs with fewer lines than some other programming languages. Python runs on an interpreter system, meaning that code can be executed as soon as it is written. This means that prototyping can be very quick. Python can be treated in a procedural way, an object-oriented way or a functional way. PYTHON SYNTAX COMPARED TO OTHER PROGRAMMING LANGUAGES Python was designed for readability, and has some similarities to the English language with influence from mathematics. Python uses new lines to complete a command, as opposed to other programming languages which often use semicolons or parentheses. Python relies on indentation, using whitespace, to define scope; such as the scope of loops, functions and classes. Other programming languages often use curly-brackets for this purpose. EXAMPLE print("Hello, World!") OUTPUT PYTHON INSTALL Many PCs and Mac s will have python already installed. To check if you have python installed on a Windows PC, search in the start bar for Python or run the following on the Command Line (cmd.exe): OUTPUT PYTHON QUICKSTART Python is an interpreted programming language, this means that as a developer you write Python (.py) files in a text editor and then put those files into the python interpreter to be executed. The way to run a python file is like this on the command line: Simple as that. Save your file. Open your command line, navigate to the directory where you saved your file, and run: THE OUTPUT SHOULD READ: PYTHON SYNTAX PYTHON INDENTATION Indentation refers to the spaces at the beginning of a code line. Where in other programming languages the indentation in code is for readability only, the indentation in Python is very important. Python us es indentation to indicate a block of code. EXAMPLE if 5 > 2: if 5 > 2: print("Five is greater than two!") print("Five is greater than two!") if 5 > 2: print("Five is greater than two!") The number of spaces is up to you as a programmer, but it has to be at least one. PYTHON COMMENTS Comments can be used to explain Python code. Comments can be used to make the code more readable. Comments can be used to prevent execution when testing code. CREATING A COMMENT Comments starts with a #, and Python will ignore them: EXAMPLE #This is a comment print("Hello, World!") EXAMPLE print("Hello, World!") #This is a comment Comments can be placed at the end of a line, and Python will ignore the rest of the line: PYTHON VARIABLES Variables are containers for storing data values. CREATING VARIABLES Python has no command for declaring a variable. A variable is created the moment you first assign a value to it. EXAMPLE OUTPUT x=5 y = "John" print(x) print(y) PYTHON VARIABLES Variables do not need to be declared with any particular type, and can even change type after they have been set. EXAMPLE x=4 # x is of type int x = "Sally" # x is now of type str print(x) OUTPUT CASTING If you want to specify the data type of a variable, this can be done with casting. EXAMPLE x = str(3) # x will be '3' y = int(3) # y will be 3 z = float(3) # z will be 3.0 OUTPUT GET THE TYPE You can get the data type of a variable with the type() function. EXAMPLE x=5 y = "John" print(type(x)) print(type(y)) OUTPUT SINGLE OR DOUBLE QUOTES? String variables can be declared either by using single or double quotes: EXAMPLE x = "John" # is the sa me as x = 'John' OUTPUT CASE-SENSITIVE Variable names are case-sensitive. EXAMPLE This will create two variables: a=4 A = "Sally" # A will not overwrite a OUTPUT PYTHON - VARIABLE NAMES A variable can have a short name (like x and y) or a more descriptive name (age, carname, total_volume). Rules for Python variables: A variable name must start with a letter or the underscore character A variable name cannot start with a number A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ ) Variable names are case-sensitive (age, Age and AGE are three different variables) EXAMPLE myvar = "John" OUTPUT my_var = "John" _my_var = "John" myVar = "John" MYVAR = "John" myvar2 = "John" ILLEGAL VARIABLE NAMES: EXAMPLE 2myvar = "John" my-var = "John" my var = "John" Remember that variable names are case-sensitive MULTI WORDS VARIABLE NAMES Variable names with more than one word can be difficult to read. There are several techniques you can use to make them more readable: CAMEL CASE Each word, except the first, starts with a capital letter: PASCAL CASE SNAKE CASE Each word starts with a capital letter: Each word is separated by an underscore character:  PYTHON VARIABLES - ASSIGN MULTIPLE VALUES Python allows you to assign values to multiple variables in one line: EXAMPLE x, y, z = "Orange", "Banana", "Cherry" print(x) print(y) print(z) OUTPUT  ONE VALUE TO MULTIPLE VARIABLES And you can assign the same value to multiple variables in one line: EXAMPLE x = y = z = "Orange" print(x) print(y) print(z) OUTPUT UNPACK A COLLECTION If you have a collection of values in a list, tuple etc. Python allows you extract the values into variables. This is called unpacking. EXAMPLE fruits = ["apple", "banana", "cherry"] x, y, z = fruits print(x) print(y) print(z) OUTPUT PYTHON - OUTPUT VARIABLES The Python print statement is often used to output variables. To combine both text and a variable, Python uses the + character: EXAMPLE x = "awesome" print("Python is " + x) OUTPUT PYTHON - OUTPUT VARIABLES You can also use the + character to add a variable to another variable: EXAMPLE x = "Python is " y = "awesome" z =x +y print(z) OUTPUT PYTHON - OUTPUT VARIABLES For numbers, the + character works as a mathematical operator: EXAMPLE x =5 y = 10 print(x + y) OUTPUT If you try to combine a string and a number, Python will give you an error: EXAMPLE x =5 OUTPUT y = 10 print(x + y) GETTING THE DATA TYPE You can get the data type of any object by using the type() function: EXAMPLE Print the data type of the variable x: x =5 print(type(x)) PYTHON NUMBERS Int Int, or integer, is a whole number, positive or negative, without decimals, of unlimited length. EXAMPLE x =1 y = 35656222554887711 z = -3255522 OUTPUT print(type(x)) print(type(y)) print(type(z)) PYTHON NUMBERS Float Float, or "floating point number" is a number, positive or negative, containing one or more decimals. EXAMPLE x = 1.10 y = 1.0 z = -35.59 OUTPUT print(type(x)) print(type(y)) print(type(z)) PYTHON NUMBERS Type Conversion You can convert from one type to another with the int(), float(), and complex() methods: EXAMPLE OUTPUT x = 1 # int y = 2.8 # float z = 1j # complex #convert from int to float: a = float(x) #convert from float to int: b = int(y) #convert from int to complex: c = complex(x) print(a) print(b) print(c) print(type(a)) print(type(b)) print(type(c)) PYTHON CASTING Specify a Variable Type There may be times when you want to specify a type on to a variable. This can be done with casting. Python is an object-orientated language, and as such it uses classes to define data types, including its primitive types. Casting in python is therefore done using constructor functions: int() - constructs an integer number from an integer literal, a float literal (by removing all decimals), or a string literal (providing the string represents a whole number) float() - constructs a float number from an integer literal, a float literal or a string literal (providing the string represents a float or an integer) str() - constructs a string from a wide variety of data types, including strings, integer literals and float literals PYTHON CASTING EXAMPLE Integers: x = int(1) # x will be 1 y = int(2.8) # y will be 2 z = int("3") # z will be 3 Floats: x = float(1) # x will be 1.0 y = float(2.8) # y will be 2.8 z = float("3") # z will be 3.0 w = float("4.2") # w will be 4.2 Strings: x = str("s1") # x will be 's1' y = str(2) # y will be '2' z = str(3.0) # z will be '3.0' PYTHON STRINGS Strings in python are surrounded by either single quotation marks, or double quotation marks. 'hello' is the same as "hello". You can display a string literal with the print() function: EXAMPLE print("Hello") print('Hello') ASSIGN STRING TO A VARIABLE Assigning a string to a variable is done with the variable name followed by an equal sign and the string: EXAMPLE a = "Hello" print(a) MULTILINE STRINGS You can assign a multiline string to a variable by using three quotes: EXAMPLE a = """Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.""" print(a) Or three single quotes: a = '''Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.''' print(a) CHECK STRING To check if a certain phrase or character is present in a string, we can use the keyword in. EXAMPLE Check if "free" is present in the following text: txt = "The best things in life are free!" print("free" in txt) OUTPUT PYTHON - MODIFY STRINGS Python has a set of built-in methods that you can use on strings. UPPER CASE EXAMPLE The upper() method returns the string in upper case: a = "Hello, World!" print(a.upper()) OUTPUT PYTHON - MODIFY STRINGS UPPER CASE EXAMPLE The lower() method returns the string in lower case: a = "Hello, World!" print(a.lower()) OUTPUT PYTHON - STRING CONCATENATION To concatenate, or combine, two strings you can use the + operator. EXAMPLE Me rge variable a with variable b into variable c: a = "Hello" b = "World" c = a +b print(c) EXAMPLE To add a space between them, add a " ": OUTPUT a = "Hello" b = "World" c = a +" " +b OUTPUT print(c) PYTHON - STRING METHODS Python has a set of built-in methods that you can use on strings. PYTHON - STRING METHODS Python has a set of built-in methods that you can use on strings. EXERCISES 1.Insert the missing indentation to make the code correct: 2. Comments in Python are written with a special character, which one? 3. Create a variable named carname and assign the value Volvo to it. 4. Create a variable called z, assign x + y to it, and display the result. EXERCISES 5. The following code example would print the data type of x, what data type would that be? 6. The following code example would print the data type of x, what data type would that be? 7. Insert the correct syntax to convert x into a floating point number. 8. Convert the value of txt to lower case.