Re: How call method from a method in same class?
Cameron,
Again, thanks for the help. I agree with everything you wrote, but... The code
was thrown together to produce the error so I could illustrate the problem. It
was by design junk. But it did produce the error, I got some great answers to
my situation, so I am very grateful for the help.
Dave,
April 1, 2019 10:30 PM, "Cameron Simpson" mailto:c...@cskk.id.au)> wrote:
On 01Apr2019 22:02, Dave mailto:dbola...@offilive.com)> wrote:
As classes get more complex, it is good to call a function to do some >of the
processing, and make
the code easier to follow. My question is >how to do that? I've attached some
silly code to
illustrate the >point. The error is: name 'validScale' is not defined. Well,
yes it >is, but maybe
not the correct way. Suggestions?
It is and it isn't. See below:
class TempConverter():
""" Temperature Converter converts a tempeature from one scale
to another scale. For example: 32, F, C will return
0 degrees C
"""
[...]
def validScale(self, scaleName):
if scaleName.upper == 'F' or 'C' or 'K':
return True
else:
return False
def convertTemp(self):
""" Converts temperature scale if scales valid."""
if validScale(self.scale):
scaleValid = True
[...]
It is an instance method, so:
if self.validScale(self.scale)
would resolve the name. However, there are several things worth discussing here.
First up, validScale itself returns a Boolean, so just return the test result.
Change:
if scaleName.upper == 'F' or 'C' or 'K':
return True
else:
return False
into:
return scaleName.upper == 'F' or 'C' or 'K'
Second, the condition is buggy. You want this:
return scaleName.upper() in ('F', 'C', 'K')
i.e. you need to call (the "()") the .upper method, and you need to check if
the result is in your
collection of valid results.
This expression:
value == A or B or C
means: True if value == A, otherwise B if B is true, otherwise C.
The next thing to observe is that you're testing whether self.scale is valid.
Normal practice would
be to make that test in __init__, and raise a ValueError if it is not so:
def __init__(self, .scale...):
if scale.upper() not in ('F', 'C', 'K'):
raise ValueError("invalid scale %r: expected one of F, C or K" % (scale,))
why recite the scale in the message? Because it makes the offending value
obvious. In particular,
if for example you called this incorrectly and had the temperature in there
instead of the scale
that will be trivial to debug from the message.
Of course, you actually want to be able to test any scal evalue for validity,
not just the one
stuffed into your instance (.scale). So lets revisit the validScale method:
def validScale(self, scale):
return scaleName.upper() in ('F', 'C', 'K')
You'll notice that it doesn't depend in "self". Or, for that matter, the class.
So this is a
"static" method: a function defined in the class for conceptual clarity, but
not with any
dependence on the class itself or a particular class instance. So:
@staticmethod
def validScale(scale):
return scaleName.upper() in ('F', 'C', 'K')
In __init__, and elsewhere, you can still call this from the instance:
def __init__(self, .scale...):
if not self.validScale(scale):
raise ValueError("invalid scale %r: expected one of F, C or K" % (scale,))
You can also call this from _outside_ the class, for example for other
validation:
scale = input("Enter a temperate scale name (F, C or K): ")
if not TempConverter.validScale(scale):
print("Bad! Bad user!")
newScaleValid = True
Again, validScale returns a Boolean. So you could have just gone:
newScaleValid = self.validScale(newScale)
if scaleValid and newScaleValid:
print('Scale converted')
else:
msg = "There was and error with the scales entered.n"
msg = msg + "You entered: " + self.scale
msg = msg + ' ' 'and' + self.newScale
print(msg)
if __name__ == "__main__":
myclass = TempConverter(32, 'f', 'c')
myclass.convertTemp()
My personal inclination would be do define a Temperature class with a convert
function to be used
like this:
temp = Temperature(32, 'f')
tempC = temp.convert('c')
This reduces the complexity of the class and IMO makes it easier to use
elsewhere.
BTW, you get an instance back from tempConverter(...), not a class. So don't
call it "myclass".
Cheers,
Cameron Simpson mailto:c...@cskk.id.au)>
--
https://mail.python.org/mailman/listinfo/python-list
Re: How call method from a method in same class?
On 4/1/19 10:29 PM, Cameron Simpson wrote:
On 01Apr2019 22:02, Dave wrote:
As classes get more complex, it is good to call a function to do some
of the processing, and make the code easier to follow. My question is
how to do that? I've attached some silly code to illustrate the
point. The error is: name 'validScale' is not defined. Well, yes it
is, but maybe not the correct way. Suggestions?
It is and it isn't. See below:
class TempConverter():
""" Temperature Converter converts a tempeature from one scale
to another scale. For example: 32, F, C will return
0 degrees C
"""
[...]
def validScale(self, scaleName):
if scaleName.upper == 'F' or 'C' or 'K':
return True
else:
return False
def convertTemp(self):
""" Converts temperature scale if scales valid."""
if validScale(self.scale):
scaleValid = True
[...]
It is an instance method, so:
if self.validScale(self.scale)
would resolve the name. However, there are several things worth
discussing here.
First up, validScale itself returns a Boolean, so just return the test
result. Change:
if scaleName.upper == 'F' or 'C' or 'K':
return True
else:
return False
into:
return scaleName.upper == 'F' or 'C' or 'K'
Second, the condition is buggy. You want this:
return scaleName.upper() in ('F', 'C', 'K')
i.e. you need to call (the "()") the .upper method, and you need to
check if the result is in your collection of valid results.
This expression:
value == A or B or C
means: True if value == A, otherwise B if B is true, otherwise C.
The next thing to observe is that you're testing whether self.scale is
valid. Normal practice would be to make that test in __init__, and raise
a ValueError if it is not so:
def __init__(self, .scale...):
if scale.upper() not in ('F', 'C', 'K'):
raise ValueError("invalid scale %r: expected one of F, C or K" %
(scale,))
why recite the scale in the message? Because it makes the offending
value obvious. In particular, if for example you called this incorrectly
and had the temperature in there instead of the scale that will be
trivial to debug from the message.
Of course, you actually want to be able to test any scal evalue for
validity, not just the one stuffed into your instance (.scale). So lets
revisit the validScale method:
def validScale(self, scale):
return scaleName.upper() in ('F', 'C', 'K')
You'll notice that it doesn't depend in "self". Or, for that matter, the
class. So this is a "static" method: a function defined in the class for
conceptual clarity, but not with any dependence on the class itself or a
particular class instance. So:
@staticmethod
def validScale(scale):
return scaleName.upper() in ('F', 'C', 'K')
In __init__, and elsewhere, you can still call this from the instance:
def __init__(self, .scale...):
if not self.validScale(scale):
raise ValueError("invalid scale %r: expected one of F, C or K" %
(scale,))
You can also call this from _outside_ the class, for example for other
validation:
scale = input("Enter a temperate scale name (F, C or K): ")
if not TempConverter.validScale(scale):
print("Bad! Bad user!")
newScaleValid = True
Again, validScale returns a Boolean. So you could have just gone:
newScaleValid = self.validScale(newScale)
if scaleValid and newScaleValid:
print('Scale converted')
else:
msg = "There was and error with the scales entered.\n"
msg = msg + "You entered: " + self.scale
msg = msg + ' ' 'and' + self.newScale
print(msg)
if __name__ == "__main__":
myclass = TempConverter(32, 'f', 'c')
myclass.convertTemp()
My personal inclination would be do define a Temperature class with a
convert function to be used like this:
temp = Temperature(32, 'f')
tempC = temp.convert('c')
This reduces the complexity of the class and IMO makes it easier to use
elsewhere.
BTW, you get an instance back from tempConverter(...), not a class. So
don't call it "myclass".
Cheers,
Cameron Simpson
Cameron,
I'm going to need a while to work through this. As I mentioned, this
was quick and dirty code just to illustrate a point - not intended to be
good code. So I'll take a close read tomorrow. Thanks again!!
Dave,
--
https://mail.python.org/mailman/listinfo/python-list
Re: How call method from a method in same class?
On 01Apr2019 22:02, Dave wrote:
As classes get more complex, it is good to call a function to do some
of the processing, and make the code easier to follow. My question is
how to do that? I've attached some silly code to illustrate the
point. The error is: name 'validScale' is not defined. Well, yes it
is, but maybe not the correct way. Suggestions?
It is and it isn't. See below:
class TempConverter():
""" Temperature Converter converts a tempeature from one scale
to another scale. For example: 32, F, C will return
0 degrees C
"""
[...]
def validScale(self, scaleName):
if scaleName.upper == 'F' or 'C' or 'K':
return True
else:
return False
def convertTemp(self):
""" Converts temperature scale if scales valid."""
if validScale(self.scale):
scaleValid = True
[...]
It is an instance method, so:
if self.validScale(self.scale)
would resolve the name. However, there are several things worth
discussing here.
First up, validScale itself returns a Boolean, so just return the test
result. Change:
if scaleName.upper == 'F' or 'C' or 'K':
return True
else:
return False
into:
return scaleName.upper == 'F' or 'C' or 'K'
Second, the condition is buggy. You want this:
return scaleName.upper() in ('F', 'C', 'K')
i.e. you need to call (the "()") the .upper method, and you need to
check if the result is in your collection of valid results.
This expression:
value == A or B or C
means: True if value == A, otherwise B if B is true, otherwise C.
The next thing to observe is that you're testing whether self.scale is
valid. Normal practice would be to make that test in __init__, and raise
a ValueError if it is not so:
def __init__(self, .scale...):
if scale.upper() not in ('F', 'C', 'K'):
raise ValueError("invalid scale %r: expected one of F, C or K" % (scale,))
why recite the scale in the message? Because it makes the offending
value obvious. In particular, if for example you called this incorrectly
and had the temperature in there instead of the scale that will be
trivial to debug from the message.
Of course, you actually want to be able to test any scal evalue for
validity, not just the one stuffed into your instance (.scale). So lets
revisit the validScale method:
def validScale(self, scale):
return scaleName.upper() in ('F', 'C', 'K')
You'll notice that it doesn't depend in "self". Or, for that matter, the
class. So this is a "static" method: a function defined in the class for
conceptual clarity, but not with any dependence on the class itself or a
particular class instance. So:
@staticmethod
def validScale(scale):
return scaleName.upper() in ('F', 'C', 'K')
In __init__, and elsewhere, you can still call this from the instance:
def __init__(self, .scale...):
if not self.validScale(scale):
raise ValueError("invalid scale %r: expected one of F, C or K" % (scale,))
You can also call this from _outside_ the class, for example for other
validation:
scale = input("Enter a temperate scale name (F, C or K): ")
if not TempConverter.validScale(scale):
print("Bad! Bad user!")
newScaleValid = True
Again, validScale returns a Boolean. So you could have just gone:
newScaleValid = self.validScale(newScale)
if scaleValid and newScaleValid:
print('Scale converted')
else:
msg = "There was and error with the scales entered.\n"
msg = msg + "You entered: " + self.scale
msg = msg + ' ' 'and' + self.newScale
print(msg)
if __name__ == "__main__":
myclass = TempConverter(32, 'f', 'c')
myclass.convertTemp()
My personal inclination would be do define a Temperature class with a
convert function to be used like this:
temp = Temperature(32, 'f')
tempC = temp.convert('c')
This reduces the complexity of the class and IMO makes it easier to use
elsewhere.
BTW, you get an instance back from tempConverter(...), not a class. So
don't call it "myclass".
Cheers,
Cameron Simpson
--
https://mail.python.org/mailman/listinfo/python-list
Re: How call method from a method in same class?
On 4/1/19 10:02 PM, Dave wrote:
As classes get more complex, it is good to call a function to do some of
the processing, and make the code easier to follow. My question is how
to do that? I've attached some silly code to illustrate the point. The
error is: name 'validScale' is not defined. Well, yes it is, but maybe
not the correct way. Suggestions?
Dave,
class TempConverter():
""" Temperature Converter converts a tempeature from one scale
to another scale. For example: 32, F, C will return
0 degrees C
"""
def __init__(self, temperature, scale, newScale):
self.temperature = temperature
self.scale = scale
self.newScale = newScale
def validScale(self, scaleName):
if scaleName.upper == 'F' or 'C' or 'K':
return True
else:
return False
def convertTemp(self):
""" Converts temperature scale if scales valid."""
if validScale(self.scale):
scaleValid = True
if validScale(self.newScale):
newScaleValid = True
if scaleValid and newScaleValid:
print('Scale converted')
else:
msg = "There was and error with the scales entered.\n"
msg = msg + "You entered: " + self.scale
msg = msg + ' ' 'and' + self.newScale
print(msg)
if __name__ == "__main__":
myclass = TempConverter(32, 'f', 'c')
myclass.convertTemp()
Thanks all for your (ready, wait for it) self-lessness help (get it?)
Dave (laughing)
--
https://mail.python.org/mailman/listinfo/python-list
Re: How call method from a method in same class?
On 4/1/19 10:12 PM, Irv Kalb wrote:
On Apr 1, 2019, at 7:02 PM, Dave wrote:
As classes get more complex, it is good to call a function to do some of the
processing, and make the code easier to follow. My question is how to do that?
I've attached some silly code to illustrate the point. The error is: name
'validScale' is not defined. Well, yes it is, but maybe not the correct way.
Suggestions?
Dave,
class TempConverter():
""" Temperature Converter converts a tempeature from one scale
to another scale. For example: 32, F, C will return
0 degrees C
"""
def __init__(self, temperature, scale, newScale):
self.temperature = temperature
self.scale = scale
self.newScale = newScale
def validScale(self, scaleName):
if scaleName.upper == 'F' or 'C' or 'K':
return True
else:
return False
def convertTemp(self):
""" Converts temperature scale if scales valid."""
if validScale(self.scale):
scaleValid = True
if validScale(self.newScale):
newScaleValid = True
if scaleValid and newScaleValid:
print('Scale converted')
else:
msg = "There was and error with the scales entered.\n"
msg = msg + "You entered: " + self.scale
msg = msg + ' ' 'and' + self.newScale
print(msg)
if __name__ == "__main__":
myclass = TempConverter(32, 'f', 'c')
myclass.convertTemp()
--
https://mail.python.org/mailman/listinfo/python-list
To answer your specific question, you call a method in the same class by
calling: self.methodName For example: self.validScale
However, once you fix that, you wind find that the if statement in that method
is not built correctly.
Also, since the variable self.scale is already set in your __init__ method,
there is no need to pass it into your function. You could just use self.scale
inside that method.
Irv
Irv,
Thanks for the response! I realize the code is junk - just done to
illustrate the problem.
Dave,
--
https://mail.python.org/mailman/listinfo/python-list
Re: How call method from a method in same class?
On 4/1/19 10:02 PM, Dave wrote:
def validScale(self, scaleName):
if scaleName.upper == 'F' or 'C' or 'K':
return True
else:
return False
def convertTemp(self):
""" Converts temperature scale if scales valid."""
if validScale(self.scale):
scaleValid = True
if validScale(self.newScale):
newScaleValid = True
if scaleValid and newScaleValid:
print('Scale converted')
else:
msg = "There was and error with the scales entered.\n"
msg = msg + "You entered: " + self.scale
msg = msg + ' ' 'and' + self.newScale
print(msg)
Note that validscale has a self parameter. Call it just
like you would from outside the class:
if self.validScale(self.newScale):
newScaleValid = True
--
https://mail.python.org/mailman/listinfo/python-list
Re: How call method from a method in same class?
> On Apr 1, 2019, at 7:02 PM, Dave wrote:
>
> As classes get more complex, it is good to call a function to do some of the
> processing, and make the code easier to follow. My question is how to do
> that? I've attached some silly code to illustrate the point. The error is:
> name 'validScale' is not defined. Well, yes it is, but maybe not the correct
> way. Suggestions?
>
> Dave,
>
> class TempConverter():
>""" Temperature Converter converts a tempeature from one scale
>to another scale. For example: 32, F, C will return
>0 degrees C
>"""
>
>def __init__(self, temperature, scale, newScale):
>self.temperature = temperature
>self.scale = scale
>self.newScale = newScale
>
>def validScale(self, scaleName):
>if scaleName.upper == 'F' or 'C' or 'K':
>return True
>else:
>return False
>
>def convertTemp(self):
>""" Converts temperature scale if scales valid."""
>if validScale(self.scale):
>scaleValid = True
>if validScale(self.newScale):
>newScaleValid = True
>if scaleValid and newScaleValid:
>print('Scale converted')
>else:
>msg = "There was and error with the scales entered.\n"
>msg = msg + "You entered: " + self.scale
>msg = msg + ' ' 'and' + self.newScale
>print(msg)
>
> if __name__ == "__main__":
>myclass = TempConverter(32, 'f', 'c')
>myclass.convertTemp()
> --
> https://mail.python.org/mailman/listinfo/python-list
>
To answer your specific question, you call a method in the same class by
calling: self.methodName For example: self.validScale
However, once you fix that, you wind find that the if statement in that method
is not built correctly.
Also, since the variable self.scale is already set in your __init__ method,
there is no need to pass it into your function. You could just use self.scale
inside that method.
Irv
--
https://mail.python.org/mailman/listinfo/python-list
How call method from a method in same class?
As classes get more complex, it is good to call a function to do some of
the processing, and make the code easier to follow. My question is how
to do that? I've attached some silly code to illustrate the point. The
error is: name 'validScale' is not defined. Well, yes it is, but maybe
not the correct way. Suggestions?
Dave,
class TempConverter():
""" Temperature Converter converts a tempeature from one scale
to another scale. For example: 32, F, C will return
0 degrees C
"""
def __init__(self, temperature, scale, newScale):
self.temperature = temperature
self.scale = scale
self.newScale = newScale
def validScale(self, scaleName):
if scaleName.upper == 'F' or 'C' or 'K':
return True
else:
return False
def convertTemp(self):
""" Converts temperature scale if scales valid."""
if validScale(self.scale):
scaleValid = True
if validScale(self.newScale):
newScaleValid = True
if scaleValid and newScaleValid:
print('Scale converted')
else:
msg = "There was and error with the scales entered.\n"
msg = msg + "You entered: " + self.scale
msg = msg + ' ' 'and' + self.newScale
print(msg)
if __name__ == "__main__":
myclass = TempConverter(32, 'f', 'c')
myclass.convertTemp()
--
https://mail.python.org/mailman/listinfo/python-list
