| Name/Number | Compulsory | Due Date | Mark |
|---|---|---|---|
| Assignment 1 | Yes | 2024-05-17 | 80.00% |
| Assignment 2 | Yes | 2024-09-23 | 0.00% |
| Assignment 3 | Yes | 2024-09-23 | 0.00% |
| Assignment 4 | Yes | 2024-09-23 | 0.00% |
| Assignment 5 | Yes | 2024-09-23 | 0.00% |
| Assignment 6 | Yes | 2024-09-23 | 0.00% |
| Assignment 7 | Yes | 2024-09-23 | 0.00% |
| Assignment 8 | Yes | 2024-09-23 | 0.00% |
Python is a popular programming language. Created by Guido van Rossum- released in 1991
It is used for-
What can Python do?
Why Python?
Good to know
Python Syntax compared to other programming languages
Python syntax can be executed by writing directly in the command line:
>>> print("Hello, World!")
Hello, World!
Or by creating a python file on the server, using the.py file extension, and running it in the Command Line:
C:UsersYour Name>python myfile.py
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 uses indentation to indicate a block of code.
Python will give you an error if you skip the indentation:
Example:
if 5 > 2:
print("Five is greater than two!")
The Correct way to write this code is;
Example:
if 5 > 2:
print("Five is greater than two!")
The number of spaces is up to you as a programmer, the most common use is four, but it has to be at least one.
In Python, variables are created when you assign a value to it, Python has no command for declaring a variable:
Example:
x = 5
y = "Hello, World!"
Python has commenting capability for the purpose of in-code documentation.
Comments start with a #, and Python will render the rest of the line as a comment:
Example:
#This is a comment
print("Hello, World!")
Comments start with a #, and Python will ignore them:
#This is a comment
print("Hello, World!")
Comments can be placed at the end of a line, and Python will ignore the rest of the line:
print("Hello, World!") #This is a comment
A comment does not have to be text that explains the code, it can also be used to prevent Python from executing code:
#print("Hello, World!")
print("Cheers, Mate!")
Python does not really have a syntax for multiline comments.
To add a multiline comment you could insert a # for each line:
#This is a comment
#written in
#more than just one line
print("Hello, World!")
Or, 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:
"""
This is a comment
written 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.
Variables are containers for storing data values
Python has no command for declaring a variable.
A variable is created the moment you first assign a value to it
x = 5
y = "John"
print(x)
print(y)
Output =
5
John
Variables do not need to be declared with any partiular type, and can even change type after they have been set.
x = 4 #x is of type int
x = "Sally" #x is now of type str
print(x)
Output =
Sally
If you want to specify the data type of a variable, this can be done with casting.
x = str(3) # x will be '3'
y = int(3) # y will be 3
z = float(3) # z will be 3.0
You can get the data type of a variable with the type() function.
x = 5
y = "John"
print(type(x))
print(type(y))
String variables can be declared either by using single or double quotes:
x = "John"
# is the same as
x = 'John'
Variable Names are case sensitive
a = 4
A = "Sally"
#A will not overwrite a
A variable can have a short name (like x and y) or a more descriptive name (age, carname, total_volume). Rules for Python variables:
Legal Variable Names
myvar = "John"
my_var = "John"
_my_var = "John"
myVar = "John"
MYVAR = "John"
myvar2 = "John"
Illegal Variable Names
2myvar = "John"
my-var = "John"
my var = "John"
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:
myVariableName = "John"
Pascal Case
- Each word starts with a capital letter:
MyVariableName = "John"
Snake Case
-Each word is separated by an underscore character:
my_variable_name = "John"
The Python print() function is often used to output variables.
x = "Python is awesome"
print(x)
Output =
Python is awesome
In the print() function, you output multiple variables, separated by a comma:
x = "Python"
y = "is"
z = "awesome"
print(x, y, z)
Output =
Python is awesome
You can also use the + operator to output multiple variables:
x = "Python "
y = "is "
z = "awesome"
print(x + y + z)
Output =
Python is awesome
Notice the space character after "Python " and "is ", without them the result would be "Pythonisawesome".
For numbers, the + character works as a mathematical operator:
x = 5
y = 10
print(x + y)
Output =
15
In the print() function, when you try to combine a string and a number with the + operator, Python will give you an error:
eg.
x = 5
y = "John"
print(x + y)
The best way to output multiple variables in the print() function is to separate them with commas, which even support different data types:
x = 5
y = "John"
print(x, y)
Variables 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.
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.
x = "awesome"
def myfunc():
x = "fantastic"
print("Python is " + x)
myfunc()
print("Python is " + x)
Output:
Python is fantastic
Python is awesome
Normally, 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.
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.
x = "awesome"
def myfunc():
global x
x = "fantastic"
myfunc()
print("Python is " + x)
In 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 |
| None Type: | NoneType |
You can get the data type of any object by using the type() function:
x = 5
print(type(x))
Output:
<class 'int'>
In Python, the data Type is set when you assign a value to a variable:
| Example | Data Type |
|---|---|
x = "Hello World" |
str |
x = 20 |
int |
x = 20.5 |
float |
x = 1j |
complex |
x = ["apple", "banana", "cherry"] |
list |
x = ("apple", "banana", "cherry") |
tuple |
x = range(6) |
range |
x = {"name" : "John", "age" : 36} |
dict |
x = {"apple", "banana", "cherry"} |
set |
x = frozenset({"apple", "banana", "cherry"}) |
frozenset |
x = True |
bool |
x = b"Hello" |
bytes |
x = bytearray(5) |
bytearray |
x = memoryview(bytes(5)) |
memoryview |
x = None |
NoneType |
If you want to specify the data type, you can use the following constructor functions:
| Example | Data Type |
|---|---|
| x = str("Hello World") | str |
| x = int(20) | int |
| x = float(20.5) | float |
| x = complex(1j) | complex |
| x = list(("apple", "banana", "cherry")) | list |
| x = tuple(("apple", "banana", "cherry")) | tuple |
| x = range(6) | range |
| x = dict(name="John", age=36) | dict |
| x = set(("apple", "banana", "cherry")) | set |
| x = frozenset(("apple", "banana", "cherry")) | frozenset |
| x = bool(5) | bool |
| x = bytes(5) | bytes |
| x = bytearray(5) | bytearray |
| x = memoryview(bytes(5)) | memoryview |
There are three numeric types in Python:
intfloatcomplexVariable of numeric types are created when you assign a value to them:
x = 1 # int
y = 2.8 # float
z = 1j # complex
To verify the type of any object in Python, use the type() function:
print(type(x))
print(type(y))
print(type(z))
Output:
<class 'int'>
<class 'float'>
<class 'complex'>
Int, or integer, is a whole number, positive or negative, without decimals, of unlimited length.
Float, or "floating point number" is a number, positive of negative, containing one or more decimals.
Float can also be scientific numbers with an "e" to indicate the power of 10.
Complex numbers are written with a "j" as the imaginary part:
x = 3+5j
y = 5j
z = -5j
print(type(x))
print(type(y))
print(type(z))
There may be times when you want to specify a type 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
