Python: Problem with raw_input reading a number [duplicate]

Question

unfortunately raw_input is not doing what I need it to do. What I am trying to do is get totPrimes = whatever I type in at the prompt. If i replace while count < totPrimes with while count < 50 this script works. If I type 50 into the prompt, this script doesnt work, I'm afraid raw_input isn't the function im looking to use? Here is a snippet of my code:

testNum = 3
div = 2
count = 1
totPrimes = raw_input("Please enter the primes: ")

while count < totPrimes :
    while div <= testNum :

Olcott

consider changing the title to something more adequate. p.e.'Problem with raw_input reading a number', or similar. – Piccaninny

FYI, this is a problem in Python 2.x, since you can compare objects of different types. In Python 3.x it will raise a TypeError: unorderable types. – Missionary

Answer 1

Do

totPrimes = int(totPrimes)
while count < totPrimes:
    # code

raw_input gives you a string you must convert to an integer or float before making any numeric comparison.

Piccaninny

Although it would be better to do that conversion before the loop and save it as a local variable. Otherwise you will be needlessly calling int each time around the loop as you do the comparison. – Viscoid

@Viscoid you are right. I wrote it that way to show the problem condensed in one line. I updated it to the more efficient version you refer. – Piccaninny

Answer 2

You need to cast totPrimes into an int like this:

integer = int(totPrimes)

Hugibert

Answer 3

You just need to convert your raw input in a integer. For your code just change your code as:

testNum = 3
div = 2
count = 1
totPrimes = raw_input("Please enter the primes: ")
totPrimes=int(totPrimes)
while count < totPrimes :
    while div <= testNum :

Hesychast

Answer 4

The raw_input function always returns a 'string' type raw_input docs, so we must in this case convert the totPrimes 'string' type to an 'int' or 'float' type like this:

totPrimes = raw_input("Please enter the primes: ")
totPrimes = float(totPrimes)

You can combine them like this:

totPrimes = float(raw_input("Please enter the primes: "))

In order to compare things in python count < totPrimes, the comparison needs to make sense (numbers to numbers, strings to strings) or the program will crash and the while count < totPrimes : while loop won't run.

You can use try/except to protect your program. managing exceptions

For people taking the course "Programming for Everybody" you can take in hours and rate this way. the if/else statement you should try to figure out.

Pyrone

Answer 5

You have to change every number to "hrs" or "rate".

For example: 40*10.50+(h-40)*10.50*1.5 is wrong, 40*r+(h-40)*r*1.5 is right.

Prearrange

Answer 6

Use input then.

Raw input returns string.

input returns int.

Diddle

No, input in Python 2 evaluates the expression. If you input a stringy expression, it will return a string. If you input a numeric expression, it will return a number (float or int depending on how exactly you expressed it). – Leonelleonelle