#flip

For starter, you can swap two variables in Python without using a temporary one:

>>> a = 3
>>> b = 5
>>> a, b = b, a
>>> print(a, b)
5 3

But above all, this function is better implemented using slices:

def flip(arr, i):
    arr[:i] = reversed(arr[:i])

Or

def flip(arr, i):
    arr[:i] = arr[i-1::-1]

#findMaxUpTo

Same here, slices and builtin functions can go a long way into simplifying the code. A "max" function that doesn't use the max builtin feels wrong to me.

A naïve rewrite would be:

def findMaxUpTo(arr, i):
    val = max(arr[:i])
    return arr.index(val)

It is good for now. But a better rewrite would make use of enumerate and the key argument of max. Possibly involving operator.itemgetter in the process and itertools.takewhile to avoid copying the array.

#pancake_sort

Not much to add here, except a note on your return value. Since you are mutating the array in-place, there is absolutely no reason to return a value. Once you call the function on an array, it will be sorted and all previous references to this array will now good the sorted version. Returning a value can mislead the users that the original array remain untouched, which is false.

Similarly, you never make use of the output variable.

#miscelaneous

Your naming style is inconsistent and some variable names don't convey much meaning, please fix it.

#flip

For starter, you can swap two variables in Python without using a temporary one:

>>> a = 3
>>> b = 5
>>> a, b = b, a
>>> print(a, b)
5 3

But above all, this function is better implemented using slices:

def flip(arr, i):
    arr[:i] = reversed(arr[:i])

Or

def flip(arr, i):
    arr[:i] = arr[i-1::-1]

#findMaxUpTo

Same here, slices and builtin functions can go a long way into simplifying the code. A "max" function that doesn't use the max builtin feels wrong to me.

A naïve rewrite would be:

def findMaxUpTo(arr, i):
    val = max(arr[:i])
    return arr.index(val)

It is good for now. But a better rewrite would make use of enumerate and the key argument of max. Possibly involving operator.itemgetter in the process and itertools.takewhile to avoid copying the array.

#pancake_sort

Not much to add here, except a note on your return value. Since you are mutating the array in-place, there is absolutely no reason to return a value. Once you call the function on an array, it will be sorted and all previous references to this array will now hold the sorted version. Returning a value can mislead the users that the original array remain untouched, which is false.

Similarly, you never make use of the output variable.

#miscelaneous

Your naming style is inconsistent and some variable names don't convey much meaning, please fix it.