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 one year ago
I am having a little trouble with this question: "Write a program using a for loop that calculates exponentials. Your program should ask the user for a base base and an exponent exp, and calculate base**exp."
This is what I came up with:
x = (raw_input ("Enter a base:"))
y = (raw_input ("Enter an exponent:"))
exponential = pow(x, y)
for solution in exponential:
print "answer =", solution
When I run it, an error comes up for line 3 with this message:
TypeError: unsupported operand type(s) for ** or pow(): 'str' and 'str'
 one year ago
I am having a little trouble with this question: "Write a program using a for loop that calculates exponentials. Your program should ask the user for a base base and an exponent exp, and calculate base**exp." This is what I came up with: x = (raw_input ("Enter a base:")) y = (raw_input ("Enter an exponent:")) exponential = pow(x, y) for solution in exponential: print "answer =", solution When I run it, an error comes up for line 3 with this message: TypeError: unsupported operand type(s) for ** or pow(): 'str' and 'str'

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c0decracker
 one year ago
Best ResponseYou've already chosen the best response.1you need to convert x and y into integer or float, because by default raw_input returns a string. You convert one variable to another type by using appropriate type conversion functions such as float() or int() See more here: http://docs.python.org/2/library/functions.html#int http://docs.python.org/2/library/functions.html#float

kah712
 one year ago
Best ResponseYou've already chosen the best response.0Thanks! I changed it from raw_input to input since I want it to be an integer..but now a new error is coming up, here is the code: x = input ("Enter a base:") y = input ("Enter an exponent:") a = pow(x, y) for solution in a: print solution and here is the error message: for solution in a: TypeError: 'int' object is not iterable

c0decracker
 one year ago
Best ResponseYou've already chosen the best response.1well, pow(x,y) returns a single number  x to the power o y. Since it's single number you can't iterate over it. You can only iterate over lists. In your case you just need to print a itself. Now mostlikely what the task question was alluding towards is that you should NOT use internal pow() function, but rather implement it yourself.

kah712
 one year ago
Best ResponseYou've already chosen the best response.0So it works when I just print a itself, so a = x**y, but I was confused because the problem stated that it should be written as a for loop, would you be able to show me what that looks like?

c0decracker
 one year ago
Best ResponseYou've already chosen the best response.1Mostlikely they want you to not use ** or pow() but calculate exponent in a loop, looking through multiplication. So let's look at example  lets say you need to compute 2 to the power of 4. You can write it out as: 2 ^ 4 = 2 * 2 * 2 * 2 See the looping here? So that's what you need to implement. I'll give you a hint and starting point: x = input ("Enter a base:") y = input ("Enter an exponent:") exponent = 1 for i in range(y): exponent = ???? so you will only need to fill in ??? :)

filiphdan
 one year ago
Best ResponseYou've already chosen the best response.0Im also still trying to solve this one without sucess...

c0decracker
 one year ago
Best ResponseYou've already chosen the best response.1@filiphdan What issues are you running into? (probably worth discussing in a separate question

kah712
 one year ago
Best ResponseYou've already chosen the best response.0c0decracker, thanks for being so thorough and helpful with your answers! I still can't figure this problem out though. First in your code why do you write exponent = 1 in the third line? I'm also not understanding how using the range function helps to translate the code into a loop. For example..if the goal is to calculate 2**4, and you use "for in in range(y)", the range of y would be (0,1,2,3) ...how do you get from there to a loop of 2 four times?

c0decracker
 one year ago
Best ResponseYou've already chosen the best response.1@kah712 Ok, so let's look at this code line by line, I am going to provide my explanation in the comments after each line: x = input ("Enter a base:") # as a result of this line x will contain a value for the base, in our example 2 y = input ("Enter an exponent:") # as a result of this line y will contain a value of the power, in our example 4 # which means that we need to multiply x by itself 4 times # so we can write this as : result = x^y = x*x*x*x exponent = 1 # to utilize the loop to calculate this we need a starting value for the result # because we are multiplying we need to have a starting value that will not # change the outcome of multiplication. What value to pick? 1 of course # because 1*anything = anything :) for i in range(y): # ok no we need to loop over multiplication 4 times. # there are 2 ways of doing it  one is a general way(see below) and # second one is "python" way, or in parlance of python developers  pythonic way :) # range() function is pythonic way of doing it. # range basically generates a list of N values(where N is the parameter you pass to it) # so if we say range(4) it will give us (0,1,2,3) so 4 values. Then we use that list to just # loop over it's values. the values are not important, what's important is that # there are 4 of them which matches exactly how many times # we need to iterate over multiplication exponent = ????

c0decracker
 one year ago
Best ResponseYou've already chosen the best response.1So the other, more general and perhaps simpler way of writing that loop is this: x = input ("Enter a base:") y = input ("Enter an exponent:") exponent = 1 i = 0 while i < y: exponent = exponent * x i = i +1 Here we are using variable i as a counter.

kah712
 one year ago
Best ResponseYou've already chosen the best response.0ah okay! So I think I'm finally understanding how the range function is working. So in our example 2^4, range(y) creates a loop of : exponent = exponent * x Which is basically exponent = 1*2 (four times). Which gives us 2*2*2*2 Thank you so so much!!!

c0decracker
 one year ago
Best ResponseYou've already chosen the best response.1Almost exactly right :) One important detail. It is actually exponent = exponent * 2 four times. So let's look at the detail of how it works: In the first iteration of the look you will have this: exponent = 1 * 2 so after that exponent will be 2 On the second iteration of the loop you will have: exponent = 2 * 2 > 4 On the third iteration: exponent = 4 * 2 > 8 And on the forth iteration: exponent = 8 * 2 > 16 Makes sense?

kah712
 one year ago
Best ResponseYou've already chosen the best response.0Yes it makes complete sense, so during the four loops, the value of "exponent" is actually changing each time it goes through a loop, taking the previous value? so if we were to do 4^3 the range would be (0,1,2) with exponent = 1, exponent = exponent * x exponent = 1*4 > exponent = 4 exponent = 4*4 > exponent = 16 exponent = 16*4 > exponent = 64 print exponent #this would print the last value of exponent, which would be 64!

c0decracker
 one year ago
Best ResponseYou've already chosen the best response.1Yes, exactly right

filiphdan
 one year ago
Best ResponseYou've already chosen the best response.0thanks for the help c0decracker, i finaly got it, it was easier than i thought, i just needed to make the exponent = exponent*x after the for cycle and it was done :)
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