Example to find all Armstrong numbers between two integers. To solve this problem, we have used nested loop and if statement.

To understand this example, you should have the knowledge of the following Python programming topics:

A positive integer is called an Armstrong number of order `n` if

abcd... = a^{n}+ b^{n}+ c^{n}+ d^{n}+ ...

For example,

153 = 1*1*1 + 5*5*5 + 3*3*3 // 153 is an Armstrong number.

Visit this page to learn how you can check whether a number is an Armstrong number or not in Python.

```
# Program to check Armstrong numbers in a certain interval
lower = 100
upper = 2000
for num in range(lower, upper + 1):
# order of number
order = len(str(num))
# initialize sum
sum = 0
temp = num
while temp > 0:
digit = temp % 10
sum += digit ** order
temp //= 10
if num == sum:
print(num)
```

**Output**

153 370 371 407 1634

Here, we have set the lower limit 100 in variable `lower` and upper limit 2000 in variable `upper`. We have used for loop to iterate from variable `lower` to `upper`. In iteration, the value of `lower` is increased by 1 and checked whether it is an Armstrong number or not.

You can change the range and test out by changing the variables `lower` and `upper`. Note, the variable `lower` should be lower than `upper` for this program to work properly.