Python
Python is developed
by Guido van Rossum in Dec 1989
Python is easy to use
Python is high level
programming language
Python is open source language
Tokens(Lexical unit)
The smallest unit of the program is called token.
The following are the tokens in Python.
Keywords,Identifiers (Names), Literals,Operators,Punctuators
Keywords:-
These are predefined reserve words that have special meaning to the language compiler or interpreter. These keywords we can not use as an identifier. Sometime it may be a command or parameter.
Identifier (Names):-
A Python identifier is a name used to identify a variable, function, class, module, or another object.
Python does not allow punctuation characters such as @, $, and % within identifiers. Python is a case sensitive programming language. Thus, System and system are two different identifiers in Python.
Here are naming conventions for Python identifiers −
Class names start with an uppercase letter. All other identifiers start with a lowercase letter.
Starting an identifier with a single leading underscore indicates that the identifier is private.
Starting an identifier with two leading underscores indicates a strongly private identifier.
If the identifier also ends with two trailing underscores, the identifier is a language-defined special name.
Examples of Vaid Identifiers:
mystr, _test,Pie,PIE,Area_triangle
Examples of InValid Identifiers
2mystr, if ,test@,xyz$
Literals
Python literals are defined as data that is given in a variable or constant
Below are the supported literals in Python
1. String Literals
String literals can be formed by enclosing a text in the quotes. We can use both single as well as double quotes to create a string
Example:
1.
"Raman" , '332'
Types of Strings:
There are two types of Strings supported in
Python:
a) Single-line String- Strings
that are terminated within a single-line are known as Single line Strings.
Example:
1.
text1='hello'
b) Multi-line String - A
piece of text that is written in multiple lines is known as multiple lines
string.
There are two ways to create multiline strings:
1) Adding black slash at
the end of each line.
Example:
1. text1='hello\
2. India'
3.
print(text1)
'helloIndia'
2) Using triple quotation
marks:-
Example:
1. str2='''''welcome
2. to
3. India'''
4.
print str2
Output:
welcome
to
India
2. Numeric literals:
Numeric Literals are immutable. Numeric literals
can belong to following four different numerical types.
|
Int(signed integers) |
Long(long integers) |
float(floating point) |
Complex(complex) |
|
Numbers(
can be both positive and negative) with no fractional part.eg: 100 |
Integers
of unlimited size followed by lowercase or uppercase L eg: 87032845L |
Real
numbers with both integer and fractional part eg: -26.2 |
In the
form of a+bj where a forms the real part and b forms the imaginary part of
the complex number. eg: 3.14j |
Example - Numeric Literals
1. x = 0b10100 #Binary Literals
2. y = 100 #Decimal Literal
3. z = 0o215 #Octal Literal
4. u = 0x12d #Hexadecimal Literal
5.
6. #Float Literal
7. float_1 = 100.5
8. float_2 = 1.5e2
9.
#Complex Literal
1 a = 5+3.14j
print(x, y, z, u)
print(float_1, float_2)
1 print(a, a.imag, a.real)
Output:
20 100 141 301
100.5 150.0
(5+3.14j) 3.14 5.0
3.Boolean literals:
A Boolean literal can have any of the two
values: True or False.
Example - Boolean Literals
1. x = (1 == True)
2. y = (2 == False)
3. z = (3 == True)
4. a = True + 10
5. b = False + 10
6.
7. print("x is", x)
8. print("y is", y)
9. print("z is", z)
print("a:", a)
print("b:", b)
Output:
x is True
y is False
z is False
a: 11
b: 10
4. Special Literals
Python contains one special literal i.e., None.
None is used to specify to that field that is
not created. It is also used for the end of lists in Python.
Example - Special Literals
1. val1=10
2. val2=None
3. print(val1)
4.
print(val2)
Output:
10
None
5.Literal Collections.
Python provides the four types of literal
collection such as List literals, Tuple literals, Dict literals, and Set
literals.
List:
- List
contains items of different data types. Lists are mutable i.e.,
modifiable.
- The
values stored in List are separated by comma(,) and enclosed within square
brackets([]). We can store different types of data in a List.
Example - List literals
1. list=['John',678,20.4,'Peter']
2. list1=[456,'Andrew']
3. print(list)
4.
print(list + list1)
Output:
['John', 678, 20.4, 'Peter']
['John', 678, 20.4, 'Peter', 456, 'Andrew']
Dictionary:
- Python
dictionary stores the data in the key-value pair.
- It
is enclosed by curly-braces {} and each pair is separated by the
commas(,).
Example
1. dict = {'name': 'Pater', 'Age':18,'Roll_nu':101}
2.
print(dict)
Output:
{'name': 'Pater', 'Age': 18, 'Roll_nu': 101}
Tuple:
- Python
tuple is a collection of different data-type. It is immutable which means
it cannot be modified after creation.
- It
is enclosed by the parentheses () and each element is separated by the
comma(,).
Example
1. tup = (10,20,"Dev",[2,3,4])
2.
print(tup)
Output:
(10, 20, 'Dev', [2, 3, 4])
Set:
- Python
set is the collection of the unordered dataset.
- It
is enclosed by the {} and each element is separated by the comma(,).
Example: - Set Literals
1. set = {'apple','grapes','guava','papaya'}
2.
print(set)
Output:
{'guava', 'apple', 'papaya', 'grapes'}
Operators
Operators are used to triggering some computation when applied to variables or other objects in an expression.
Arithmetic Operators :- +,-,/,//,*,%
Bitwise Operators:- & , ^, |
Shift Operators:- >> <<
Identity Operators :- is , is not
relational operators:- >,<,>=,<=,!=
logical Operators:- and ,or, not
Membership Operators:- in, not in
Arithmetic Assignment:- /=,+=,*=,//=,
Punctators
These are the symbols that are used in the programming language to organize the sentence structure
eg
#,@,:,[]
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