Construct simple examples in the Python shell to illustrate that you understand the concepts above.

Download and experiment with demo.py until you understand it fully. Why can the alternate$\_$case function be called with either one or two arguments? How would you explain what the alternate$\_$case function does to someone who knows nothing about computer science?

Write a function named double$\_$integer that repeatedly asks the user to enter an integer until a non$-$negative integer is entered. The function should then return twice the integer's value. For example, the user might enter "apple", then $"3\mathrm{.}14",$ then $"-34",$ then $"34".$ In this example, the function should return $68.$

def alternate$\_$case $($sentence$,$ start $=0)$:

result $=""$

upper $=$ True

for i in range$($len$($sentence$))$:

if i $<$ start:

result $=$ result $+$ sentence$[$i$]$

elif upper:

result $=$ result $+$ sentence$[$i$].$upper$()$

else:

result $=$ result $+$ sentence$[$i$].$lower$()$

upper $=$ not upper

return result

###

def double$\_$integer$()$:

###

print$($alternate$\_$case$("$abcdefghij$"))$

print$($alternate$\_$case$("$abcdefghij$",2))$

print$($alternate$\_$case$("$abcdefghij$",3))$

print$($alternate$\_$case$("$ABCDEFGHIJ$"))$

print$($alternate$\_$case$("$ABCDEFGHIJ$",3))$

print$($alternate$\_$case$("$ABCDEFGHIJ$",4))$