Knowledge in python programming
Multi Line Comments
Multi Line CommentsPython does not really have a syntax for multi line comments.To add a multiline comment you could insert a # for each line:Example #This is a comment#written in#more than just one lineprint("Hello, World!")
Jay Kakadiya
Multi Line Comments 2
Multi Line Comments 2Or, not quite as intended, you can use a multiline string.Since Python will ignore string literals that are not assigned to a variable, you can add a multiline string (triple quotes) in your code, and place your comment inside it:Example """This is a commentwritten in more than just one line"""print("Hello, World!") As long as the string is not assigned to a variable, Python will read the code, but then ignore it, and you have made a multiline comment.
Python Variables
Python VariablesCreating VariablesVariables are containers for storing data values.Unlike other programming languages, Python has no command for declaring a variable.A variable is created the moment you first assign a value to it.Example x = 5 y = "John" print(x) print(y) 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) String variables can be declared either by using single or double quotes:Example x = "John"# is the same asx = 'John'
Global Variables
Global VariablesVariables that are created outside of a function (as in all of the examples above) are known as global variables.Global variables can be used by everyone, both inside of functions and outside.ExampleCreate a variable outside of a function, and use it inside the function x = "awesome" def myfunc(): print("Python is " + x)myfunc() If you create a variable with the same name inside a function, this variable will be local, and can only be used inside the function. The global variable with the same name will remain as it was, global and with the original value.ExampleCreate a variable inside a function, with the same name as the global variable x = "awesome" def myfunc(): x = "fantastic" print("Python is " + x)myfunc() print("Python is " + x)
The global Keyword
The global KeywordNormally, when you create a variable inside a function, that variable is local, and can only be used inside that function.To create a global variable inside a function, you can use the global keyword.ExampleIf you use the global keyword, the variable belongs to the global scope: def myfunc(): global x x = "fantastic"myfunc() print("Python is " + x) Also, use the global keyword if you want to change a global variable inside a function.ExampleTo change the value of a global variable inside a function, refer to the variable by using the global keyword: x = "awesome"def myfunc(): global x x = "fantastic"myfunc() print("Python is " + x)
Python Data Types
Python Data TypesBuilt-in Data TypesIn programming, data type is an important concept.Variables can store data of different types, and different types can do different things.Python has the following data types built-in by default, in these categories: Text Type: str Numeric Types: int, float, complex Sequence Types: list, tuple, range Mapping Type: dict Set Types: set, frozenset Boolean Type: bool Binary Types: bytes, bytearray, memoryview Getting the Data TypeYou can get the data type of any object by using the type() function:ExamplePrint the data type of the variable x: x = 5 print(type(x))
Python Numbers
Python NumbersPython NumbersThere are three numeric types in Python:intfloatcomplexVariables of numeric types are created when you assign a value to them:Example x = 1 # inty = 2.8 # floatz = 1j # complex To verify the type of any object in Python, use the type() function:Example print(type(x))print(type(y))print(type(z))
python numbers
IntInt, or integer, is a whole number, positive or negative, without decimals, of unlimited length.ExampleIntegers: x = 1y = 35656222554887711z = -3255522print(type(x))print(type(y))print(type(z)) FloatFloat, or "floating point number" is a number, positive or negative, containing one or more decimals.ExampleFloats: x = 1.10y = 1.0z = -35.59print(type(x))print(type(y))print(type(z)) Float can also be scientific numbers with an "e" to indicate the power of 10.ExampleFloats: x = 35e3y = 12E4z = -87.7e100print(type(x))print(type(y)) print(type(z))
Complex
ComplexComplex numbers are written with a "j" as the imaginary part:ExampleComplex: x = 3+5jy = 5jz = -5jprint(type(x))print(type(y)) print(type(z)) Type ConversionYou can convert from one type to another with the int(), float(), and complex() methods:ExampleConvert from one type to another: x = 1 # inty = 2.8 # floatz = 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))
Random Number
Random Numberython does not have a random() function to make a random number, but Python has a built-in module called random that can be used to make random numbers:ExampleImport the random module, and display a random number between 1 and 9: import randomprint(random.randrange(1,10))
Python Casting
Python CastingSpecify a Variable TypeThere 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 rounding down to the previous whole number), 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 literalsExampleIntegers: x = int(1) # x will be 1 y = int(2.8) # y will be 2 z = int("3") # z will be 3 ExampleFloats: 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 ExampleStrings: x = str("s1") # x will be 's1' y = str(2) # y will be '2' z = str(3.0) # z will be '3.0'
String Methods
String MethodsPython has a set of built-in methods that you can use on strings.ExampleThe strip() method removes any whitespace from the beginning or the end: a = " Hello, World! " print(a.strip()) # returns "Hello, World!" ExampleThe lower() method returns the string in lower case: a = "Hello, World!" print(a.lower()) ExampleThe upper() method returns the string in upper case: a = "Hello, World!" print(a.upper()) ExampleThe replace() method replaces a string with another string: a = "Hello, World!" print(a.replace("H", "J")) ExampleThe split() method splits the string into substrings if it finds instances of the separator: a = "Hello, World!" print(a.split(",")) # returns ['Hello', ' World!']