I have just started learning Python. I am trying to have the user input a number base, and a number, and convert that to decimal.
I've been trying to use the built in int function like this:
base = raw_input("what number base are you starting with? \n")
num = raw_input("please enter your number: ")
int(num,base)
My problem is that when you use that int function, the number your converting needs to be in quotes like so: int('fff',16)
How can I accomplish this when im using a variable?
Quotes are not needed. The quotes are not part of the string.
>>> int('fff',16)
4095
>>> da_number = 'fff'
>>> int(da_number, 16)
4095
You will, however, need to cast the base to an integer.
>>> base = '16'
>>> int(da_number, base) # wrong! base should be an int.
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: an integer is required
>>> int(da_number, int(base)) # correct
4095
The result of raw_input() will be a string, I think your issue is actually that base is still a string when you need it to be an integer.
Try the following:
base = raw_input('base? ')
num = raw_input('num? ')
print int(num, int(base))
For example:
>>> base = raw_input('base? ')
base? 16
>>> num = raw_input('num? ')
num? fff
>>> print int(num, int(base))
4095
The problem isn't quotes. The problem is with data types. int with a base expects an integer base and a string number. So, in your case, you'd use:
int(num,int(base))
This takes the strings which are returned from raw_input and it constructs a suitable base from the base string while leaving num as a string as required by the int function.
The quotes are there to tell Python that those characters should be interpreted as the contents of a String, not as language syntax.
When you have a variable, Python already knows that the contents are a string. Not only do you not need the quotes, but adding them would confuse Python into thinking that you wanted a string holding the name of the variable.
So, both this:
int('fff',16)
and this:
someNumber = 'fff'
int(someNumber,16)
are doing the same thing as far as the int() function is concerned.
All that being said, int() can take a string or a number for the value, but must have a number for the base. So, since raw_input always returns a string, you'd need to do something more like:
base = raw_input("what number base are you starting with? \n")
num = raw_input("please enter your number: ")
int(num,int(base))
str(number), for examplestr(10)will return'10'.