Data Structure is a core concept of computer science by which we can do programming in any other progrmming languages. Data structure are used to store the data elements in a sequential manner.
In Python we can call Data Structure as Collections. Collections are containers that are used to store collections of data.
- List
- Dictionary
- Tuple
- Set
A List is used to store the sequence of various types of data. Data are inclosed inside [ ] brackets seprated by commas(,). Lists are mutable in nature it means data which can be changed when required. Duplicate entries are allowed in list. A list can also have another list as an item. This is called a nested list.
list1 = [ ] #Empty List
list2 = [ sequence1 ]
list3 = [ sequence1, sequence2, sequence3 ]
language = ['C','C++','Java','Python'] //List of Strings
number = [3,5,4,9] //List of Numbers
mixed = ['Mango','Apple',1,'Banana',8] //List of Mixed Data Type
nested = [['Raman', 'Nikhil'],[2,5,7]] //List of Nested List
deep_nested = ['Honey','Deepak',[1,5,8,['Akshay','Shubham',['India','Australia]]]] //Deeply Nested
- Each element in the list has a position in the list known as an index. The list index starts from zero.
| Element | Index |
|---|---|
| 23461 | 0 |
| 77194 | 1 |
| 10295 | 2 |
| 14920 | 3 |
- Index positions actually help us to directly access a value from the list. list_name[index] can be used to directly access the list element at the mentioned index position.
- If we want to access an element directly, we can also use it to directly modify an element in the list. element[1] = 23413
| Python Expression | Result | Operation |
|---|---|---|
| [1,2,3]+[8,9,9] | [1,2,3,8,9,9] | Concatination |
| len([4,5,6]) | 3 | Length |
| 7 in [1,4,7] | True | Membership |
| for n in [1,3,5]: print (n) | 1 3 5 | Iteration |
| n=[1,3,7] print(n[2]) | 7 | Indexing: Offset Starts at 0 |
| n=[1,3,7] print(n[-2]) | 3 | Negative Slicing: Count from right |
| n=[1,3,7] print(n[1:]) | [3,7] | Slicing |
| Function | Description |
|---|---|
| cmp(list1,list2) | Compare elements of both list |
| len(list) | Give total Length of list |
| max(list) | Return item from list with maximum value |
| min(list) | Return item form list with minimum value |
| list(seq) | converts a tuple to list |
| list.append(obj) | Append object obj to list |
| list.count(obj) | Return count of how many times obj occurs in list |
| list.insert(index,obj) | Insert object obj to list at offset index |
| obj=list.pop() | Remove the item at position -1 from list and assigns it to obj |
| list.remove(obj) | Removes object obj from list |
| list.reverse() | Reverses the order of items in list |
| sorted(list) | Sorts item in list |