DATA, EXPRESSIONS, STATEMENTS IN PYTHON PROGRAMMING

python

1. DATA, EXPRESSIONS, STATEMENTS UNIT 2

2. List data type List is an ordered sequence of items Values in the list are called elements/items Lists are created by placing all items inside a square bracket separated by commas Items in a list can be of different data type Lists are mutable

3. Operations on List Indexing Slicing Concatenation Repetitions Updation , Insertion and Deletion

4. Creating a List List1=["python",7.79,101,"hello"] List2=["god",6.78,9] Indexing print(List1[0]) python print(List1[2]) 101 Slicing (ending position-1) print(List1[1:3]) [7.79, 101] print(List1[1:]) [7.79, 101, 'hello'] Repetition print(List2*3) ['god', 6.78, 9, 'god', 6.78, 9, 'god', 6.78, 9] Concatenation print(List1+List2) ['python', 7.79, 101, 'hello', 'god', 6.78, 9] Updating the List List1[2]=45 print(List1) ['python', 7.79, 45, 'hello'] Inserting an element List1.insert(2,"program") print(List1) ['python', 7.79, 'program', 45, 'hello'] Removing an element List1.remove(45) print(List1) ['python', 7.79, 'program', 'hello']

5. Tuple A tuple is a container which holds a series of comma- separated values (items or elements) between parentheses Tuples are immutable It can hold a mix of data types ( int , float, string, list) Tuples are faster than lists Example: tuple1 = (element1, element2, element 3…….element n) tuple1 = (1, 2, 3, 4, 5) tuple2 = (‘a’, ‘b’, ‘c’, ‘d’)

6. Creating a tuple t=("python",7.79,101,"hello") Indexing print(t[0]) python Slicing print(t[1:3]) (7.79, 101) Concatenation t+("ram",67) ('python', 7.79, 101, 'hello', 'ram', 67) Repetition print(t*2) ('python', 7.79, 101, 'hello', 'python', 7.79, 101, 'hello')

7. Sets A set is an unordered collection of items. Every element is unique and cannot be changed. A set id created by placing all the items (elements) inside curly braces {}, separated by comma.

8. my_set ={1,3} print( my_set ) my_set.add (2) # add an element print( my_set ) my_set.update ([2,3,4]) # add multiple elements print( my_set ) my_set.update ([4,5],{1,6,8}) # add list and set print( my_set ) my_set.discard (4) # discard an element in a set print( my_set ) my_set.remove (6) # remove an element print( my_set ) my_set.pop () # pop 1st element from a set print( my_set )

9. Dictionary Python dictionary is a container of unordered set of elements like list. The elements are surrounded by curly braces {}. Elements in Dictionaries are accessed via keys and not by their position. The values of a dictionary can be of any type. Keys must be immutable data types such as strings, numbers or tuples.

10. dict ={'Name':'John','SSN':4568,'Designation':'Manager'} print( dict ['Name']) print( dict ['SSN']) print( dict ['Designation']) dict ['Designation']='Senior Manager' dict ['Location']="Delhi" print("After Updating") print( dict ) print( len ( dict ))

11. Boolean Type  A Boolean type represents special values ‘True’ and ‘False’. They are represented as 1 and 0, and can be used in numeric expressions as value. The most common way to produce a Boolean value is with a relational operator.   Example: 2 < 3 is True

12. Tokens: A token is the smallest unit of the program Keywords Variables Literals Delimiter Operators

13. Keywords Keywords are reserved words they have a predefined meanings in Python Python has 33 keywords

14. Variables A variable is a memory location where a programmer can store a value. Example: roll_no , amount, name etc. No prior declaration is required. The interpreter allocates the memory on the basis of the data type of a variable.

15. Rules of naming variables Variable name must begin with only letter (a-z, A-Z) or underscore (_) Keywords cannot be a variable No special symbols allowed No blank spaces are allowed between variable names Variable names are case sensitive

16. Literals A literal is a notation that represents a fixed value Numeric Literals They Consist of digits (0-9) with an optional (+ or -) possibly a decimal point Examples of integer literals Floating point Literals Range of the numeric literal 10 -308 to 10 308 10 2500 -4500 +200

17. Arithmetic Overflow error a=1.4e200 b=2.1e200 c=a*b print(c)

18. String Literals String Literals represent sequence of characters Example: “Hello” It can be ‘ (single quote) or double quotes (“ ”)

19. DELIMITERS Delimiters are symbols that perform three special roles in Python like grouping, punctuation, and assignment/ binding of objects to names. Table presents all 24 of Python’s delimiters. Delimiters of Python Delimiters Classification ( ) [ ] { }     Grouping . , : ; @       Punctuation = +=  = *= /= //= %= **= Arithmetic assignment/ binding &= != ^= <= >>=       Bit wise assignment/ binding

20. Tuple Assignment An assignment to all of the elements in a tuple using single assignment statement The left side is a tuple of variables; the right side is a tuple of values. Naturally, the number of variables on the left and the number of variables on the right have to be the same

21. >>> T1 = (10, 20, 30) >>> T2 = (100,200,300,400) >>> print (T1) (10, 20, 30) >>> print (T2) (100, 200, 300, 400) >>> T1, T2=T2, T1 >>> print (T1) (100, 200, 300, 400) >>> print (T2) (10, 20, 30)

22. Comments Comments make the program easily understandable by the programmer and non-programmer who are seeing the code Comment statements are non-executable statements so they are ignored while program execution They have no effect on the program results Example: # swap.py # Swapping the values of two variable program # written by G.Sugitha , April 2018 Another way of doing comments is to user triple quotes “”” or ‘’’ Example ‘’’ This is also a Perfect example for Multi-line comments’’’