Using range() to generate list of numbers in Python
problem
You’re learning Python and wish to combine range with for loop. In this post we will see an example of this combination and how useful it is.
SOLUTION
The range is a built-in function that generates a range type. For example a range of values, starting from 0. We can generate 5 numbers with the following code.
r = range(5) # generate 5 numbers starting from 0
The numbers generated are from 0 (inclusive) to 5(exclusive). More specific: 0,1,2,3,4. If we try to print the range it won’t show any values but the following.
r = range(5) # generate 5 numbers starting from 0
print(r)
OUTPUT
Converting range to a list
r = range(5) # generate 5 numbers starting from 0
nums = list(r) # convert range to a list of numbers
print(nums)
OUTPUT
Converting range to a set
r = range(5) # generate 5 numbers starting from 0
nums = set(r) # convert range to a set of numbers
print(nums)
output
Using a range on for loop
One of the benefits of range() is that it is iterable. This mean we can iterate over it by using a loop mechanism like for-loop. For example to print 10 numbers we can do the following:
for num in range(10):
print(num)
The code above will iterate over the range of 10 numbers and print the following:
output
Parameters of range
By default range generates numbers from 0 to the number we pass as argument (exclusive). For example as we saw above, range(5) will generate values: 0,1,2,3,4. Each successor number in the range is incremented by 1. This is also added by default.
Changing the range
To create a custom range we can pass 2 parameters. The first parameter is the starting number and the second the ending number (exclusive). For example to generate numbers from 1 to 10 inclusive we can do the following:
nums_1_to_10 = range(1,11)
If we wish to change the step (the number added to the successor) we can pass it as 3rd parameter.
Generate even numbers using range
For example, let’s generate a range of all even numbers from 0 to 10.
even = range(0,10,2) # generates 0,2,4,6,8
The 10 is exclusive so it won’t make it to the range.
Generate odd numbers using range
Let’s generate a range of odd numbers from 1 to 10.
odd = range(1,10,2) # generates 1,3,5,7,9
If we wish to print them in a row as a list, we simply convert the range to list as follows:
print(list(odd))
use of Range in synopsis
There are 3 ways of using range():
- range(a) # generates numbers from 0 to a-1, incremented by 1
- range(a,b) # generates number from 0 to b-1, incremented by 1
- range(a,b,c) # generates numbers from a to b-1, incremented by c
conclusion
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Ellion
Professional IT consultant, writer, programmer enthusiast interested in all sorts of coding.
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