Question

this is with regards to the hashing and classes lecture. The lecture code shows
def readVal(valType, requestMsg, errorMsg):
numTries = 0
while numTries < 4:
val = raw_input(requestMsg)
try:
val = valType(val)
return val
except ValueError:
print(errorMsg)
numTries += 1
raise TypeError('Num tries exceeded')
_--------------------------------------
why does
val = valType(val)
results in an exception ValueError if my valType is int. and my val is a float example 2.9
isnt val = suppose to be an assignment of an object to a value?

Answer 1

First of all I want to spread mccornacks word:
In order to make it possible to have spaces preserved when copying you can enter
```
on a new line
and it is the ` on the ~-button (followed by an Enter)
to get a block started where you can copy your code into

def readVal(valType, requestMsg, errorMsg):
numTries = 0
while numTries < 4:
val = raw_input(requestMsg)
try:
val = valType(val)
return val
except ValueError:
print(errorMsg)
numTries += 1
raise TypeError('Num tries exceeded')

# MAIN
print readVal(int, 'Enter int: ', 'Not an int.')

```
That way anybody can copy and paste the code without having to edit line ends and idents etc. back in

Answer 2

I'm still working on ps4 so a few more lectures to go.

However I think that anything you enter is in assigned to val as a string.
the print readVal(int, ..., ...) assigns int to valType
and in the try-part the value of val is assigned if it can be converted safely to the required type
a float cannot ingeneral be assigned to an integer without being changed

if you would execute
print readVal(float, ..., ...)
any integer value is turned to its floating point equivalent

I can't find the formal description valType() on internet either

Answer 3

Oh, and to start the block with ``` on a new line
That dissapeared in my first message over here

Answer 4

valType is what the user enters into the function . e.g readVal(int(valtype), "enter an int","not an int")

Answer 5

Well, I might be able to give a better anwer once I've don lecture 10, but I'm still struggeling to do problem 4b, so that will not be versy soon I'm afraid.
Hopefully somebody else will come to the rescue