Peter Anderson wrote:
<div class="moz-text-flowed" style="font-family: -moz-fixed">Hi!
I am trying to teach myself how to program in Python using Zelle's
"Python Programming: An Introduction to Computer Science" (a very good
text). At the same time I have decided to start with Python 3 (3.1.1).
That means that I have to convert Zelle's example code to Python 3
(which generally I cope with).
I'm hoping that somebody can help with what's probably a very simple
problem. There is a quadratic equation example involving multiple user
inputs from the one "input" statement. The code works fine with Python
2.5 but when I convert it to Python 3 I get error messages. The code
looks like:
05 import math
06
07 def main():
08 print("This program finds the real solutions to a quadratic\n")
09
10 a, b, c = input("Please enter the coefficients (a, b, c): ")
11
12 '''
13 a = int(input("Please enter the first coefficient: "))
14 b = int(input("Please enter the second coefficient: "))
15 c = int(input("Please enter the third coefficient: "))
16 '''
17
18 discrim = b * b - 4 * a * c
19 ...
25 main()
Lines 08 to 12 are my Python 3 working solution but line 06 does not
work in Python 3. When it runs it produces:
Please enter the coefficients (a, b, c): 1,2,3
Traceback (most recent call last):
File "C:\Program Files\Wing IDE 101
3.2\src\debug\tserver\_sandbox.py", line 25, in <module>
File "C:\Program Files\Wing IDE 101
3.2\src\debug\tserver\_sandbox.py", line 10, in main
builtins.ValueError: too many values to unpack
>>>
Clearly the problem lies in the input statement. If I comment out line
10 and remove the comments at lines 12 and 16 then the program runs
perfectly. However, I feel this is a clumsy solution.
Could somebody please guide me on the correct use of "input" for
multiple values.
Regards,
Peter
The input() function in Python3 produces a string, and does not evaluate
it into integers, or into a tuple, or whatever. See for yourself by trying
print ( repr(input("prompt ")) )
on both systems.
You can subvert Python3's improvement by adding an eval to the return value.
a, b, c = eval(input("Enter exactly three numbers, separated by commas"))
is roughly equivalent to Python 2.x input expression. (Python 3's
input is equivalent to Python 2.x raw_input)
DaveA
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