Slice Operator in Python

 

Slice Operator

in slice operator, :(colon) is used

It is separated in 3 sections to read data from a sequence

A sequence can be  List, Tuple, Dictionary and String

    [start : end-1 : step]

lets suppose we have a string as sequence below (name is a string)

 name = "Techno Xpresss"

 

case 1 : [ :  : ]

• without passing any value

• by default 
• start is 0th index
• end-1 will be last index
• step will 1

• it will print all the data in sequence from start to end

 #program

 name = "Techno Xpresss"
 print (name[ : : ])

 #output
 Techno Xpresss

case 2 : [start : : ]

• we can pass only start

• by default 
• end-1 will be last index
• step is 1

• it will print data till end in sequence from the start position

 #program

 name = "Techno Xpresss"
 print (name[7: : ])
 
 #output
 Xpresss

case 3 : [ : end-1 : ]

• we can pass only end value.

• by default
• start is 0th index
• step is 1

• it will print data from starting to passed end position-1

 #program

 name = "Techno Xpresss"
 print (name[ :7: ])
 
 #output
 Techno 

case 4 :[ : : step]

• we can pass only steps.

• by default
• start is 0th index
• end-1 will be last index

• It will print data from start to end by passed taking passed step.

 #program

 name = "Techno Xpresss"
 print (name[ : :2])

 #output
 Tcn pes

case 5 :[start : end-1 : step]

• we can call all three.

• every thing will be taken for respective position

• It will print data starting from passed start position to passed end position -1 and with the passed step

 #program

 name = "Techno Xpresss"
 print (name[0:12: ])
 print (name[0:12:3])
 print (name[0:12:4])


 #output
 Techno Xpres
 Th r
 Tnp

So we can try many combination, but conclusion  is if values were not passed it will take default values.

Lets have look at negative indexing as well

 #program

 name = "Techno Xpresss"
 print (name[-14:-2: ])

 #output
 Techno Xpres

printing in reverse

 #program

 name = "Techno Xpresss"
 print (name[14: :-1])
 print(name[ : :-1])
 print(name[-1 : -15: -1])

 #output
 ssserpX onhceT
 ssserpX onhceT
 ssserpX onhceT

you can play more by changing values, for a better understanding.