Solve the programming task below in a Python markdown code block.
We have an integer array with unique elements and we want to do the permutations that have an element fixed, in other words, these permutations should have a certain element at the same position than the original.

These permutations will be called: **permutations with one fixed point**.

Let's see an example with an array of four elements and we want the permutations that have a coincidence **only at  index 0**, so these permutations are (the permutations between parenthesis):
``` 
arr = [1, 2, 3, 4]
      (1, 3, 4, 2)
      (1, 4, 2, 3)
Two permutations matching with arr only at index 0
``` 

Let's see the permutations of the same array with only one coincidence at index **1**:
``` 
arr = [1, 2, 3, 4]
      (3, 2, 4, 1)
      (4, 2, 1, 3)
Two permutations matching with arr only at index 1
```
Once again, let's see the permutations of the same array with only one coincidence at index **2**:
``` 
arr = [1, 2, 3, 4]
      (2, 4, 3, 1)
      (4, 1, 3, 2)
Two permutations matching with arr only at index 2
```
Finally, let's see the permutations of the same array with only one coincidence at index **3**:
``` 
arr = [1, 2, 3, 4]
      (2, 3, 1, 4)
      (3, 1, 2, 4)
Two permutations matching with arr only at index 3
```
For this array given above (arr) :

- We conclude that we have 8 permutations with one fixed point (two at each index of arr).

- We may do the same development for our array, `arr`, with two fixed points and we will get `6` permutations.

- There are no permutations with coincidences only at three indexes.

- It's good to know that the amount of permutations with no coincidences at all are `9`. See the kata Shuffle It Up!!

In general:

- When the amount of fixed points is equal to the array length, there is only one permutation, the original array.

- When the amount of fixed points surpasses the length of the array, obvously, there are no permutations at all.

Create a function that receives the length of the array and the number of fixed points and may output the total amount of permutations for these constraints.

Features of the random tests:
```
length of the array = l
number of fixed points = k
10 ≤ k ≤ l ≤ 9000
```
See the example tests!
Enjoy it!!

Ruby versin will be released soon.

#Note: This kata was published previously but in a version not well optimized.
Also feel free to reuse/extend the following starter code:
```python
def fixed_points_perms(n,k):
```