Python Revision Tour
Mrs. MADHUMITA RANI
P.G.T (Computer Science )
J.N.V. Bangalore Urban
Introduction
Python revision Tour - 1
Python revision Tour - 2
��Python used as general purpose, high level programming language. Developed by Guido van Rossum in 1991.��
Pros of Python :
�Cons of Python�
Data types in Python
1. Number
2. String
3. Boolean
4. List
5. Tuple
6. Set
7. Dictionary
Number
In Python we use number data type to store numeric value.
Input : a = complex(5) Output : (5+0j)
print(a)
String
Ex : - Input :
str='computer science’
print('str-', str) # print string
Output :
str- computer science
String Method
Method | Description |
Capitalize() | Returns a copy of string with its first character as capita |
Find() | Returns the lowest index in the string |
Isalnum() | Returns true if the character in the string are alphanumeric |
Isalpha() | Returns true if the character in the string are alphabetic |
Isdigit() | Returns true if the character in the string are digit |
Islower() | Returns true if all the cased characters in the string are lowercase |
Isupper() | Returns true if all the cased characters in the string are uppercase |
Title() | Returns True if the string is in title case |
Swapcase() | Returns a copy of the string with uppercase character converted to lowercase and vice versa |
Partition() | Splits the string at the first occurrence of argument |
String Methods contd..
Method | Description |
Isspace() | Returns true if there are only whitespace character in the string |
Count() | Returns the number of non-overlapping occurrence of substring in the given string |
lstrip | Returns a copy of the string with leading characters removed |
rstrip | Returns a copy of the string with trailing characters removed |
Startswith() | Returns true if string starts with the argument otherwise return false |
Endswith() | Returns true if string ends with the argument otherwise return false |
Lower() | Returns a copy of string converted to lowercase |
Upper() | Returns a copy of string converted to uppercase |
Title() | Returns a titlecase version of the string |
Boolean
It is used to store two possible values either true or false.
e.g. a=“jnv"
b=str.isupper() # test if string contains upper case
print(b)
Output : False
LIST
List are collections of items and each item has its own index value.
List Methods
Method | Description |
Index() | Returns the index of first matched item from the list |
Append() | Adds an item to the end of the list |
Extend() | Adds list at the end |
Insert() | Insert any item in between the list |
Pop() | Remove an item from the list |
Remove() | Remove the first occurrence of the given element |
Clear() | Remove all the items from the list |
Count() | Returns the count of the item that passes as argument |
Reverse() | Reverses the item of the list |
Sort() | Sort the item of the list, by default in increasing order |
Tuples
Example: 1) t1 = (1,2,3,4,5,6)
2) t2 = (‘A’ , ‘B’ , ‘C’)
3) t3 = (‘a’ , ‘b’ , 1,2,3,4,5,6)
Tuple Methods
Method | Description |
Len() | Return the length of tuple |
Max() | Returns the element from the tuple having maximum value |
Min() | Returns the element from the tuple having minimum value |
Index() | Returns the index of an existing element of a tuple |
Count() | Returns the count of the member element / object in a given sequence( list/tuple) |
Tuple() | Constructor method, create tuple |
Dictionary
e.g. dict = {'Subject': 'comp sc', 'class': '11’}
print(dict)
print ("Subject : ", dict['Subject’])
print ("class : ", dict.get('class’))
Output
{'Subject': 'comp sc', 'class': '11’}
Subject : comp sc class : 11
class : 11
Dictionary Method
Method | Description |
len() | Returns length of the dictionary |
clear() | Remove all method from the dictionary |
get() | Get the item with the given key |
has_keys | To check the presence of given key in the dictionary |
items() | Return all the items of the dictionary |
key() | Return all the keys in the dictionary |
value() | Returns all the values from the dictionary in the form of list in no particular order |
update() | This will merge the key : value pairs from a new dictionary, adding or replacing as needed |
cmp | Compare to dictionary based on their elements |
List
example : (1) a = [1,2,3,4,5]
(2) b = [‘A’ , ‘B’ , ‘C’]
(3) c = [1,2, ’A’ , ‘B’ ]
Mutable and Immutable
Mutable data type can change the value
Immutable data type can’t be change value
Arithmetic Operators
Operators are special symbols in Python that carry out arithmetic or logical computation. The value that the operator operates on is called the operand.
Arithmetic operators Used for mathematical operation
Operator Meaning Example
+ Add two operands x + y +2
* Multiply two operands x * y
/ Divide left operand by the right one x / y
% Modulus - remainder of the division x % y
// Floor division - division that results into whole number x // y
** Exponent - left operand raised to the power of right x**y
Comparison operators - Used to compare values
Operator Meaning Example
> Greater than - True if x is greater than y x > y
< Less that - True if x is less than y x < y
== Equal to - True if both operands are equal x == y
!= Not equal to - True if operands are not equal x != y
>= Greater than or equal to - True if left operand
is greater than or equal to the right x >= y
<= Less than or equal to - True if left operand
is less than or equal to the right x <= y
Logical Operator
Operator Meaning Example
and True if both the operands are true x and y
or True if either of the operands is true x or y
not True if operand is false not x
Operators Precedence
Operator~ + - | Description |
** | Exponentiation (raise to the power) |
~ + - | Complement, unary plus and minus (method names for the last two are +@ and -@) |
* / % // | Multiply, divide, modulo and floor division |
+ - | Addition and subtraction |
>> << | Right and left bitwise shift |
& | Bitwise 'AND' |
^ | | Bitwise exclusive `OR' and regular `OR' |
<= < > >= | Comparison operators |
<> == != | Equality operators |
= %= /= //= -= += *= **= | Assignment operators |
is is not | Identity operators |
in not in | Membership operators |
not or and | Logical operators |
| |
Python Function and Module
Python function :
1. Build in unction
2. Function defined in module
3. User defined function.
Python Module :
Statements Flow Control
Control statements are used to control the flow of execution depending upon the specific condition.
a. if statements
b. if-else statements
c. Nested if-else statement
2. Iteration statements (LOOPS)
a. While Loop
b. For Loop
c. Nested For Loops
3. Jump statements ( Break, continue, Pass )
If Statements
An if statement is a programming conditional statement that, if proved true, performs a function or displays information.
Input | Output |
x=1 y=2 if(x==1 and y==2): print(‘Matched') | Matched |
if-else Statements
and some other code if the test expression is false.
Input | Output |
a=10 if(a < 100): print(‘less than 100') else: print(‘more than equal 100') | less than 100 |
Nested if-else statement
The nested if...else statement allows you to check for multiple test expressions and execute different codes for more than two conditions.
Input | Output |
num = float(input("Enter a number: ")) if num >= 0: if num == 0: print("Zero") else: print("Positive number") else: print("Negative number") | Enter a number: 4 Positive number |
Iteration Statements (Loops)
While Loop
It is used to execute a block of statement as long as a given condition is true. And when the condition become false, the control will come out of the loop. The condition is checked every time at the beginning of the loop.
While – else
It is used to execute a block of statement as long as a given condition is true. And when the condition become false, it execute else part of block of statements and come out of the loop.
Input (While ) | Output |
x = 1 while (x <= 4): print(x) x = x + 1 | 1 2 3 4 |
Input (While-else) | Output |
i = 0 while i < 4: i += 1 print(i) else: print("Break\n") | 1 2 3 4 Break |
For Loop
Continue Statement: It returns the control to the beginning of the loop
Break Statement: It brings control out of the loop.
Pass Statement: We use pass statement to write empty loops. Pass is also used for empty control statements, function and classes.
Input | Output |
for letter in ‘rajeev': if letter == 'e' or letter == ‘a': continue print( letter)
| r J v |
Input | Output |
for letter in 'rajeev': if letter == 'a' or letter == 'j': break print('Current Letter :', letter) | Current Letter : a |
for letter in 'rajeev': pass print('Last Letter :', letter) | Last Letter : v |