From the documentation:
range([start], stop[, step])
The start defaults to 0, the step can be whatever you want, except 0 and stop is your upper bound, it is not the number of iterations. So declare n to be whatever your upper bound is correctly and you will not have to add 1 to it.
e.g.
>>> for i in range(1, 7, 1): print(i)
...
1
2
3
4
5
6
>>> for i in range(1, 7, 2): print(i)
...
1
3
5
A nice feature, is that it works in reverse as well.
>>> for i in range(7, 0, -1): print(i)
...
7
6
5
4
3
2
1
If you aren't using it as an index but for something that can have positive or negative values, it still comes in handy:
>>> for i in range(2, -3, -1): print(i)
...
2
1
0
-1
-2
>>> for i in range(-2, 3, 1): print(i)
...
-2
-1
0
1
2
python - Pythonic way to iterate through a range starting at 1 - Stack Overflow
Interpret "for i in n" as "for i in range(n)" if n is an int - Ideas - Discussions on Python.org
What does "for i in range" mean in Python?
python - Understanding range() in a for loop - Stack Overflow
Videos
From the documentation:
range([start], stop[, step])
The start defaults to 0, the step can be whatever you want, except 0 and stop is your upper bound, it is not the number of iterations. So declare n to be whatever your upper bound is correctly and you will not have to add 1 to it.
e.g.
>>> for i in range(1, 7, 1): print(i)
...
1
2
3
4
5
6
>>> for i in range(1, 7, 2): print(i)
...
1
3
5
A nice feature, is that it works in reverse as well.
>>> for i in range(7, 0, -1): print(i)
...
7
6
5
4
3
2
1
If you aren't using it as an index but for something that can have positive or negative values, it still comes in handy:
>>> for i in range(2, -3, -1): print(i)
...
2
1
0
-1
-2
>>> for i in range(-2, 3, 1): print(i)
...
-2
-1
0
1
2
range(1, n+1) is not considered duplication, but I can see that this might become a hassle if you were going to change 1 to another number.
This removes the duplication using a generator:
for _ in (number+1 for number in range(5)):
print(_)
So, I had a question where I was supposed to find the sum of the first natural numbers using Python.
Here's the problem:
Write a program to find the sum of the cubes of the first n natural numbers, where the value of n is provided by the user.
And this is the code that my professor used to allow the interpreter to produce the result:
= int(input("Enter a number:"))
sum = 0
for i in range (n+1): sum = sum + i*i*i
# for i in range starts as a loop, and then tries to get to (n + 1), whatever that may be
print("the sum of the first", n, "integers is", sum)
However, I can't seem to understand what "for i in range (n + 1): sum = sum + i * i * i" means. In other words, I don't understand what role this part of the code is doing to produce the result. Especially, I don't understand what the role of "for i in range (n + 1)" is doing. Does anyone mind explaining this to me?
When you call range() with two arguments, the first argument is the starting number, and the second argument is the end (non-inclusive). So you're starting from len(list_of_numbers), which is 5, and you're ending at 6. So it just prints 5.
To get the results you want, the starting number should be 0, and the end should be len(list_of_numbers)+1. If you call it with one argument, that's the end, and 0 is the default start. So use
for i in range(len(list_of_numbers)+1):
or if you want to pass the start explicitly:
for i in range(0, len(list_of_numbers)+1):
range gives you and iterator between (start, end) end not included.
So in your case the iterator is (start=len(list_of_numbers), end=6).
Since len(list_of_numbers) = 5, this translates to range(5,6) which is 1 element, 5, since 6 is excluded.
https://docs.python.org/3/library/functions.html#func-range
I'm a Python beginner and wondering if anyone can explain what the for j in range i line is doing here? In addition, what is the proper name for these i and j expressions?
n=5;
for i in range(n):
for j in range(i):
print ('* ', end="")
print('')
for i in range(n,0,-1):
for j in range(i):
print('* ', end="")
print('')