# Python Code Example: nested for-loop

In the following program, a nested loop is used to check how often the loops are run through.

This code defines four variables: `a`, `b`, `c1`, and `c2`, and assigns values to `a` and `b` (`5` and `7`, respectively). `c1` and `c2` are both set to `0`.

The code then enters a nested loop structure, where an outer loop (`for i in range(20, a, -1)`) runs 20 times, decrementing `i` by `1` each time. For each iteration of the outer loop, `c1` is incremented by `1`.

The inner loop (`for j in range(0, b)`) runs `b` times (in this case, `7` times), incrementing `j` by `1` each time. For each iteration of the inner loop, `c2` is incremented by `1`.

The code then checks if `i` is equal to `j`, and if so, it prints a message indicating how many times each loop has run, along with the values of `c1` and `c2`. The message states that `c1` represents the number of times the outer loop has run, and that `c2` represents the number of times the inner loop has run (`c1` multiplied by `b`).

It’s important to note that, in this code, `i` and `j` will never be equal, so the message will not be printed.

``````a, b, c1, c2 = 5, 7, 0, 0

for i in range(20, a, -1):
c1 = c1 + 1
for j in range(0, b):
c2 = c2 + 1
if i == j:
print("How many times the loops are run?")
print(
"first loop: "
+ str(c1)
+ "\nsecond loop: "
+ str(c2)
+ " ("
+ str(c1)
+ " * "
+ str(b)
+ ")"
)``````
##### Output
``````How many times the loops are run?
first loop: 15
second loop: 105 (15 * 7)``````