- What is a Programming Language?
- Why Python?
- Comments
- Python Variables
- Data Types
- Operators
- Type Casting in Python
- Python Strings
- Lists
- Tuples
- Sets
- Dictionaries
- Conditions
- Loops
- Functions
A programming language is an artificial language that can be used to control the behaviour of a machine, particularly a computer. Programming languages, like human languages, are defined through the use of syntactic and semantic rules, to determine structure and meaning respectively.
- Versatile: It is used in web development, data science and artificial intelligence and automation etc.
- Pyhton is equipped of libraies like pandas numpy and framework ....
- Free and open source
- Easy to learn
- Portable
- A lot of applications including web developing, app developing and data science
- Can be treated in a procedural way, object oriented way and fuctional way
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.
- Single line comment #
- Multi-line comment ''' '''
Variables are containers for storing data values.
Python has no command for declaring a variable. There is no need to write the data type of a variable before it.
A variable is created the moment you first assign a value to it.
Following are some built-in data types in Python:
- Text Type:
str--> " " - Numeric Types:
int,float--> 123, 12.97683 - Sequence Types:
list,tuple--> [1,3,4,5] , (1,8,6,4) - Mapping Type:
dict--> {} - Set Type:
set--> {[ ]} - Boolean Type:
bool--> TRUE and FALSE
Operators are used to perform operations on variables and values. Python divides the operators in the following groups:
-
Arithmetic operators
-
Assignment operators
-
Comparison operators
-
Logical operators
-
Membership operators
- Addition +
- Subtraction -
- Multiplicatin *
- Division /
- Modulus %
- Exponential **
- Floor Division //
paranthesis
exponentiation
multiplication / division / f.d / modulus
addition, subtraction
Assignment operators are used to assign values to variables
These are used to compare two variables with each other.
">" is greater than
"<" is smaller than
">=" is greater than or equal to
"<=" is smaller than or equal to
"==" is equal to
"!=" is not equal to
Python has three Boolean operators, or logical operators: and , or , and not.
Logical operators are used to combine conditional statements
and Returns "True" if both statements are true
or Returns "True" if one of the statements is true
not Reverse the result, returns "False" if the result is true
Membership operators are used to test if a sequence is presented in an object
in Returns "True" if a sequence with the specified value is present in the object
not in Returns "True" if a sequence with the specified value is not present in the object
Identity operators are used to compare the objects, not if they are equal, but if they are actually the same object, with the same memory location.
is Returns True if both variables are the same object
is not Returns True if both variables are not the same object
We can change the data type of a variable or a value.
- implicit typecasting
- explicit typecasting
Strings in python are surrounded by either single quotation marks, or double quotation marks.
You can display a string literal with the print() function
You can assign a multiline string to a variable by using three quotes or three single quotes:
The line breaks are inserted at the same position as in the code.
To concatenate, or combine, two strings you can use the "+" operator.
Like many other popular programming languages, strings in Python are arrays of bytes representing unicode characters.
However, Python does not have a character data type, a single character is simply a string with a length of 1.
Square brackets can be used to access elements of the string.
You can return a range of characters by using the slice syntax.
Specify the start index and the end index, separated by a colon, to return a part of the string. There are three values separated by a colon(:) that can be used in slicing. And all of them are optional.
Syntax= string[start:end:step]
Python has a set of built-in methods that you can use on strings.
Upper Case
The upper() method returns the string in upper case:
Lower Case
The lower() method returns the string in lower case:
Capitalize
The capitalize() method returns the string with first character capitalized:
Sorted
The sorted function is used to sort the string alphabatically.
Join
join() is used to join characters of a list in the form of string separated by the specified character.
Count
The count method is used to count the occurences of a specific character or substring in a string.
endswith
It checks whether a string ends with a specified character.
startswith
It checks whether a string starts with a specified character.
endswith
It checks whether a string ends with a specified character.
find
It checks at what position a specified character is present.
Lists are used to store multiple items in a single variable.
List items are ordered, changable, allow duplicate values.
List items can be of any data type.
Use len() function to determine how many items a list has.
We can add items in the list using:
append()methodinsert()methodextend()method
We can remove items from list using:
-
remove()method -
pop()method -
delkeyword -
clear()method
You cannot copy a list simply by typing list2 = list1, because: list2 will only be a reference to list1, and changes made in list1 will automatically also be made in list2.
There are ways to make a copy, one way is to use the built-in List method copy().
Another way to make a copy is to use the built-in method list().
If there is a sublist within a list, it is known as nested list. We can access the elements of nested list by using its indexes.
Tuples are used to store multiple items in a single variable.
A tuple is a collection which is ordered and unchangeable.
Tuples are written with round brackets.
Items in the tuples can be accessed by entering the index number inside square bracket.
The index can be a positive index, a negative index or a range of the indices.
Tuples are immutable. You can't add or remove items in it. However, there are some hacks to do that.
If you want to multiply the content of a tuple a given number of times, you can use the * operator.
Python has two built-in methods for tuple.
-
count()method -
index()method
Like lists and tuples, sets are used to store multiple values of different data types in a single variable.
Set items are unordered, unindexed, unchangable and don't allow duplicate values.
(Set items are unmutable, we can still add and remove items).
Sets are written with curly brackets.
To determine how many items a set has, use the len() function.
You cannot access items in a set by referring to an index or a key.
But you can loop through the set items using a for loop, or ask if a specified value is present in a set, by using the in keyword.
Once a set is created, you cannot change its items, but you can add new items.
To add an item to a set, use the add() method.
To add items from another set into the current set, use the update() method.
intersection_update()intersection()symmetric_difference()difference()
Dictionaries are used to store data values in key:value pairs.
Dictionary items are ordered, changable, and do not allow duplicates.
Dictionaries are written with curly brackets, and have keys and values.
There is no concept of indexes in dictionary. It is an ordered object but we cannot access elements by using its number indexes. For accessing dictionary elements, we use keys. These keys map the values present against them in dictionary.
In case of dictionary values, duplicates are allowed. But duplication of keys is not allowed.
-
If we use same key two times in a dictionary, the value against that key gets updated and the former value get discarded. And the dictionary will contain only one key of that name.
-
Key is a unique identifier that is used to map a specific value present against it in the dictionary. It cannot be duplicated. You cannot use same key to map two different values.
In dictionary, we can use membership operators to know whether a key present in a dictionary or not. It cannot be used to check values in dictionary.
- clear() It is used to clear data from a dictionary.
- keys() It is used to get a list of all the keys present in a dictionary.
- values() It is used to get a list of all the values present in a dictionary.
- item() It is used to get all the elements of a dictionary.
- get() It is used to get specified keys' value from a dictionary.
To remove elements from a dictionary, following methods are used:
- pop() It is used to remove specified element from a dictionary.
- popitem() It is used to remove last element from a dictionary. It takes no argument.
Conditions are used in program when we want to execute a specific portion of that on the basis of the incoming input.
The statement next to a condition will only excecute if it's true otherwise it'll be ignored by the interpretor.
Keywords:
if
elif
else
If we want to perform few steps of a program repeatedly, we will use loops instead of writing these lines each time.
Loops make the program more efficient.
In python, no braces are used to separate a block of statemments from the whole program. On the other hand, proper indentations are used for this purpose.
Two types of loops are used in python.
- For loop
- while loop
Functions allow us to create blocks of code that can be easily executed many times without needing to constantly rewrite the entire block of code.
There are a lot of built-in functions in python that make programming more easier and efficient.
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Prepared by Safwan
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