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
Python3
lis1 = list ( range ( 6 ))
lis2 = list ( range ( 3 , 6 ))
lis3 = list ( range ( - 6 , 2 ))
print ( "List generated using 1 parameter : " + str (lis1))
print ( "List generated using 2 parameters : " + str (lis2))
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
Python3
print ( "List generated using step : " +
str ( list ( range ( 3 , 10 , 2 ))))
print ( "List generated using negative step : " +
str ( list ( range ( 10 , - 5 , - 3 ))))
print ( "List generated using step, value constraints fail : " +
str ( list ( range ( 10 , - 5 , 3 ))))
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 constraints 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
Last Updated :
05 Aug, 2021
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