Python Slicing

Pradeep

Python Slicing

Python Slicing provide a concise way to create sub list, sub string from the existing list and strings respectively without using loop statement or if clauses. Slicing works in similar way for both Strings & Lists.

Slicing statement must have 2 paramater separated by colon to specify start & end position, and 3rd optional parameter also separated by colon to specify the increment.


Syntax: list_or_string_object[start_position : end_position : step]

Start_Position: If start position is not specified then it will start from initial index of the object(list/string).
End_Position: If end position is not specified then it will go till end of the object). Remember end_position index will be excluded and it will consider only till end_position-1 index.
Step: Step will determine the value of increment from the starting position. If step is not specified then default increment will be one (1).

➠ Examples of String slicing

Example 1: Start position is 0 & end position is 4, therefore output is DBMS
```
a_str = 'DBMSTUTORIALS'
print(a_str[0:4])

Output: DBMS
```
Example 2: Start position is 4 & end position is not specified, therefore it went till end of the string and resulting in output TUTORIALS.
```
a_str = 'DBMSTUTORIALS'
print(a_str[4:])

Output: TUTORIALS
```
Example 3: Start position is not specified & end position is also not specified, therefore it will start from beginning and till end of the string.
```
a_str = 'DBMSTUTORIALS'
print(a_str[:])

Output: DBMSTUTORIALS
```
Example 4: Start position is 0, end position is -1 and increment by 2 , Last 'S' is not included in the output because end position will consider till end_position-1 so actual end will be -2.
```
a_str = 'DBMSTUTORIALS'
print(a_str[0:-1:2])

Output: DMTTRA
```

Example 5: Reversing string by using step value as -1


a_str = 'DBMSTUTORIALS'
print(a_str[::-1])

Output: SLAIROTUTSMBD

➠ Examples of List slicing

Example 1: Start position is 0 & end position is 4, therefore output is ['D', 'B', 'M', 'S']


a_list = ['D', 'B', 'M', 'S', 'T', 'U', 'T', 'O', 'R', 'I', 'A', 'L', 'S']
print(a_list[0:4])

Output: ['D', 'B', 'M', 'S']

Example 2: Start position is 4 & end position is not specified, therefore it went till end of the list and resulting in output ['T', 'U', 'T', 'O', 'R', 'I', 'A', 'L', 'S']
```
a_list = ['D', 'B', 'M', 'S', 'T', 'U', 'T', 'O', 'R', 'I', 'A', 'L', 'S']
print(a_list[4:])

Output: ['T', 'U', 'T', 'O', 'R', 'I', 'A', 'L', 'S']
```

Example 3: Start position is not specified & end position is also not specified, therefore it will start from beginning and till end of the list.


a_list = ['D', 'B', 'M', 'S', 'T', 'U', 'T', 'O', 'R', 'I', 'A', 'L', 'S']
print(a_list[:])

Output: ['D', 'B', 'M', 'S', 'T', 'U', 'T', 'O', 'R', 'I', 'A', 'L', 'S']

Example 4: Start position is 4, end position is -1 and increment by 2 , 'S' is not included in the output because end position will consider till end_position-1 so actual end will be -2.
```
a_list = ['D', 'B', 'M', 'S', 'T', 'U', 'T', 'O', 'R', 'I', 'A', 'L', 'S']
print(a_list[4:-1:2])

Output: ['T', 'T', 'R', 'A']
```

Example 5: Reversing list by using step value as -1


a_list = ['D', 'B', 'M', 'S', 'T', 'U', 'T', 'O', 'R', 'I', 'A', 'L', 'S']
print(a_list[::-1])

Output: ['S', 'L', 'A', 'I', 'R', 'O', 'T', 'U', 'T', 'S', 'M', 'B', 'D']

Python Slicing

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Python Slicing