Python | range() method

There are many iterables in Python like list, tuple etc. range() gives another way to initialize a sequence of numbers using some conditions.

range() is commonly used in for looping hence, knowledge of same is key aspect when dealing 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 >=0 and list[n] = 0 and list[n] > 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 : Demonstrating range() without step parameter

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# Python3 code to demonstrate the 
# working of range() without step
  
# using range()
lis1 = list(range(6))
lis2 = list(range(3, 6))
lis3 = list(range(-6, 2))
  
# initializing list using range, 1 parameter
# only stop parameter
print("List generated using 1 parameter : " + str(lis1)) 
  
# initializing list using range, 2 parameters
# only step and stop parameters
print("List generated using 2 parameters : " + str(lis2)) 
  
# initializing list using range, 2 parameter
# only step and stop parameters
print("List generated using 2 parameters with negatives : " + str(lis3)) 

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Output:


List generated using 1 parameter : [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 : Demonstrating range() using step











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# Python 3 code to demonstrate the  


# working of range() with step 


  


# initializing list using range 


# using step 


print("List generated using step : " +


    str(list(range(3, 10, 2))))  


  


# initializing list using range 


# using negative step 


print("List generated using negative step : " +


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


  


# initializing list using range 


# using negative step, 


# value contraints fail case 


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


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


  


# initializing list using range 


# using 0 step 


# error  


print("List generated using 0 step : " +


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



















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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






    

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