Python | range () method



range() is usually used for loops, so knowing the same is key when working with any kind of Python code.

Syntax: range (start, stop, step)

Parameters:
start: Element from which sequence constructed has to start. (default: 0)
stop: Element number at which numbers in sequence have to end (exclusive).
step: Can be + ve or -ve number, denoting the elements need to be skipped during filling of list. (default: 1)

Returns: The list using the formula:
list [n] = start + step * n (for both positive and negative step) where , n & gt; = 0 and list [n] = 0 and list [n] & gt; stop (for negative step)

Returns ValueError if step is 0. Value constraint is checked in case of step, failing to meet returns empty sequence, else returns sequence according to formula.

Code # 1: Demonstration of range () without step parameter

# Python3 demo code
# working range () without step

 
# using range ()

lis1 = list ( range ( 6 ))

lis2 = list ( range ( 3 , 6 ))

lis3 = list ( range ( - 6 , 2 ))

  
# list initialization using a range, 1 parameter
# stop parameter

print ( "List generated using 1 parameter: " + str (lis1)) 

  
# initialize the list using a range, 2 parameters
# only step and stop parameters

print ( "List generated using 2 parameters: " + str (lis2)) 

 
# list initialization using a range, 2 parameters
# only step and stop parameters

print ( "List generated using 2 parameters with negatives:" + str (lis3)) 

Output:

 List generated using 1 p arameter: [0, 1, 2, 3, 4, 5] List generated using 2 parameters: [3, 4, 5] List generated using 2 parameters with negatives: [-6, -5, -4, -3, - 2, -1, 0, 1] 

Code # 2: Demonstration of range () using a step

# Python 3 demo code
# working range () in increments

 
# initializing the list using a range
# using a step

print ( "List generated using step:" +

str ( list ( range ( 3 , 10 , 2 ))) ) 

 
# list initialization using a range
# using a negative step

print ( "List generated using negative step:" +

str ( list ( range ( 10 , - 5 ,  - 3 ))))

 
# initializing the list using a range
# using a negative step
# the value does not match the case

print ( "List generated using step, value contraints fail:" +

str ( list ( range ( 10 , - 5 , 3 ))))

 < / code> 
# initialize the list using a range
# using step 0
# error

print ( "List generated using 0 step:" +

str ( list ( range ( 3 , 7 , 0 ))))

Output:

 List generated using step: [3, 5, 7, 9] List generated using negative step: [10, 7, 4, 1, -2] List generated using step, value contraints fail: [ ] 
Exception:

 Traceback (most recent call last): File "/home/bdae725dff7b38d3681eee38f6a6d434.py", line 23, in print ("List generated using 0 step:" + str (list (range (3 , 7, 0)))) ValueError: range () arg 3 must not be zero