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Often times we want to create a list containing a continuous value like, in a range of 100-200. Let’s discuss how to create a list using the
range[] function.
Will this work ?
My_list = [range[10, 20, 1]]
print[My_list]
Output :
As we can see in the output, the result is not exactly what we were expecting because Python does not unpack the result of the range[] function.
Code #1: We can use argument-unpacking operator i.e. *.
My_list = [*range[10, 21, 1]]
print[My_list]
Output :
As we can see in the output, the argument-unpacking operator has successfully unpacked the result of the range function.
Code #2 : We can use the
extend[] function to unpack the result of range function.My_list = []
start, end = 10, 20
if start < end:
My_list.extend[range[start, end]]
My_list.append[end]
print[My_list]
Output
:
Given two numbers r1 and r2 [which defines the range], write a Python program to create a list with the given range [inclusive].
Examples:
Input : r1 = -1, r2 = 1 Output : [-1, 0, 1] Input : r1 = 5, r2 = 9 Output : [5, 6, 7, 8, 9]
Let’s discuss a few approaches to Creating a list of numbers with a given range in Python.
Naive Approach using a loop
A naive method to create a list within a given range is to first create an empty list and append the successor of each integer in every iteration of for loop.
Python3
def createList[r1, r2]:
if [r1 == r2]:
return r1
else:
res =
[]
while[r1 < r2+1 ]:
res.append[r1]
r1 += 1
return res
r1, r2 = -1, 1
print[createList[r1, r2]]
Output:
[-1, 0, 1]
Using List comprehension
We can also use list comprehension for the purpose. Just iterate ‘item’ in a for loop from r1 to r2 and return all ‘item’ as list. This will be a simple one liner code.
Python3
def createList[r1, r2]:
return [item for item in range[r1, r2+1]]
r1, r2 = -1, 1
print[createList[r1, r2]]
Output:
[-1, 0, 1]
Using Python range[]
Python comes with a direct function range[] which creates a sequence of numbers from start to stop values and print each item in the sequence. We use range[] with r1 and r2 and then convert the sequence into list.
Python3
def createList[r1, r2]:
return list[range[r1, r2+1]]
r1, r2 = -1, 1
print[createList[r1, r2]]
Output:
[-1, 0, 1]
Using numpy.arange[]
Python numpy.arange[] returns a list with evenly spaced elements as per the interval. Here we set the interval as 1 according to our need to get the desired output.
Python3
import numpy as np
def createList[r1, r2]:
return
np.arange[r1, r2+1, 1]
r1, r2 = -1, 1
print[createList[r1, r2]]
Output:
[-1, 0, 1]
Using numpy to create list of numbers with given range
Here we are creating a list of numbers from a given range with the defined increment.
Python3
import numpy as np
def fun[start, end, step]:
num =
np.linspace[start, end,[end-start]
*int[1/step]+1].tolist[]
return [round[i, 2] for i in num]
print[fun[1,5,0.5]]
Output:
[1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0]