This question already has answers here:
Why does adding a trailing comma after an expression create a tuple?
(6 answers)
What is the syntax rule for having trailing commas in tuple definitions?
(10 answers)
Closed 1 year ago.
I was trying to create a new class just today so I can organize pygame code (Learning Pygame/First Project) After making and setting up the class I realized that it had turned all of my parameter type variables into a tuple for no reason. I created a new py file for testing and created to different classes in it with the same everything (however one was copied from my other code the other wasnt) and for some stupid reason the one copied was a tuple and the one made from scratch wasnt. I tested it out some more and found that copying the innit function from the tuple one would result in a tupled variable. I also know that it isn't a part of my IDE due to me testing it in the python console seperate from my IDE and the same issue occured. All I can do now is ask you for your help and provide pictures and my code.
class Person:
def __init__(self, yaxis):
self.yaxis = yaxis
p = Person(64)
print(p.yaxis)
class Player:
def __init__(self, yaxis):
self.yaxis = yaxis,
p1 = Player(64)
print(p1.yaxis)
Output:
p = 64
p1 = (64,)
IDE Image Code Image
Console Code
When you set the yaxis variable in the Player class, you have an extra comma at the end which causes python to automatically convert the variable to a tuple.
Related
This question already has answers here:
Shadows name xyz from outer scope
(5 answers)
What is the problem with shadowing names defined in outer scopes?
(10 answers)
Closed 1 year ago.
I am learning Python and am trying to take concepts that I learn from video tutorials and add to them. I just watched a video on If Statements and Comparisons, and I wanted to add to what was done in the video by getting input from the user. I received the "shadows name 'ans' from outer scope" warning and have seen others ask this question on the site, but their examples do not involve getting input from the user. Thank you in advance for your help!
ans = input("What color is the sky? ")
def color(ans):
if ans == str("Blue"):
return str("Correct!")
else:
return str("Incorrect.")
print(color(ans))
First things first - the warning is specific to pycharm and your code should run correctly as it is.
Now, there are two ways how you can get rid of the warning:
Either you can rename the argument used within the function i.e. instead of giving it same name ans, you can opt for a different name e.g. answer.
The other way could be suppress this warning in pycharm:
# noinspection PyShadowingNames
def color(ans):
# rest of the code...
This question already has answers here:
How can I get the source code of a Python function?
(13 answers)
Closed 4 years ago.
I recently asked a question with title "python find the type of a function" and got very helpful answers. Here is a related question.
Suppose I import *.py files written by me, and these imports result in f being one of the functions defined by me. Now I write to my python interpreter x = f. Later, I want to see the full definition of f, preferably with comments still in place, knowing only x. Is this possible? Does python remember which file the definition was imported from, which is, of course, not enough to give the full definition of f, unless one can find the actual relevant definition?
The built in help(object) will give you the correct documentation if you alias k to some function you commented - same for inspect.getsource(k) - they know which function is ment by your variable name alias k at this time.
See:
the help() built in
inspect.getsource(k)
(taken from here)
Example:
# reusing this code - created it for some other question today
class well_documented_example_class(object):
"""Totally well documented class"""
def parse(self, message):
"""This method does coool things with your 'message'
'message' : a string with text in it to be parsed"""
self.data = [x.strip() for x in message.split(' ')]
return self.data
# alias for `parse()`:
k = well_documented_example_class.parse
help(k)
Prints:
Help on function parse in module __main__:
parse(self, message)
This method does coool things with your 'message'
'message' : a string with text in it to be parsed
Same goes for inspect.getsource(k):
# from https://stackoverflow.com/a/52333691/7505395
import inspect
print(inspect.getsource(k))
prints:
def parse(self, message):
"""This method does coool things with your 'message'
'message' : a string with text in it to be parsed"""
self.data = [x.strip() for x in message.split(' ')]
return self.data
You should think of the way Python uses variables. You have objects (can be classes, functions, lists, scalars or whatelse) and variables that only hold references to those objects.
That explains why when multiple variables point to the same mutable object, if you change it through one of those variables, the change in visible in all other ones.
This is the same thing here. The function object manages all its attributes: its docstring, its code, and its source (if it has: C function show no source). Assigning the function to a new variable does not hide the object behind anything: you still access the original object.
Things would go differently with decorators, because the decorator creates a new object, and the original object is only available to the decorated one.
This question already has answers here:
How can you dynamically create variables? [duplicate]
(8 answers)
Closed 4 years ago.
I have a class for which I want to create instances through a function, but I also want to be able to name the instances with the value of a Tkinter.Entry widget.
The simplified version of that I am trying to achieve is the following:
class vtdiagram():
IO=0.0
IC=0.0
EO=0.0
EC=0.0
IGA=0.0
def printvtvalues(self):
print self.IO
print self.IC
print self.EO
print self.EC
print self.IGA
def createvtinstance():
global Nametemp
Nametemp=vtdiagram()
If I run this code, then I can call Nametemp.printvtvalues() and get all values printed, so it works fine.
I am now trying to change the name of the instance Nametemp to the string that is on the Tkinter entry widget. Basically, if engine1 is written on the entry box when I createvtinstance(), I would like to then call the instance by:
engine1.printvtvalues()
and get the values.
I imagine the function should look something like this:
def createvtinstance():
global Nametemp
Nametemp=vtdiagram()
Nametemp._command_to_change_the_name_=stringinentrybox.get()
Do you guys have know of a command that can do such a thing?
Or is there a way that I could achieve the same effect, maybe using a dictionary?
***edit: The reason I need to name the variables is for the following (in plain English): I am creating an 'engine simulator'.
The idea is that the user will enter engine parameters -plus its name- in a GUI and this is the vtdiagram class.
The reason for using a class is that I have the characteristics of 'engine1, engine2...' saved as an instance of the class but I also need to have functions attached to it. This is because I want to generate graphs and diagrams of saved engines but only when called. So I can compare engine1 and engine2, but then get 'forget' engine2 from the GUI to compare 1 and 3.
Please keep in mind I am quite new to python :) ***
Many thanks!
Juan
I wouldn't recommend changing the name of a variable based on user input.
You could "achieve the same effect" like this:
Objects=[]
Names=[]
def createvtinstance(Object=4,Name="engine1"):
global Nametemp
global Objects
global Names
Nametemp=Object # I'll just use an int to demonstrate.
Objects+=[Nametemp]
Names+=[Name]
def Use(Name="engine1"):print(Objects[Names.index(Name)]) # Or: Objects[Names.index(Name)].SomeFunction()
If you REALLY want to alter the name of a variable based on user input, then you could do it like this:
def createvtinstance(Name="engine1"):
if (not Name[0]in"qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM") or False in(i in"1234567890qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM"for i in Name) or Name in("tkinter","createvtinstance","Name","vtdiagram",):return "Invalid name." # This should make the code more "robust".
try:exec("global "+Name+"\n"+Name+"=vtdiagram()")
except SyntaxError:return "Invalid name."
Or this:
def createvtinstance(Name="engine1"):
if (not Name[0]in"qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM") or False in(i in"1234567890qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM"for i in Name) or Name in("tkinter","createvtinstance","Name","vtdiagram",):raise NameError("The name "+Name+" does not comply to validation rules.") # This should make the code more "robust".
try:exec("global "+Name+"\n"+Name+"=vtdiagram()")
except SyntaxError:raise NameError(Name+" is a reserved keyword.")
The top example shows how you would use a list to find an object in another list; using a string. This is what I'd probably do in this situation, however a dictionary could be better.
The bottom examples show how you would actually name a variable based on user input. This is NOT RECOMMENDED. Everyone seems to agree that using exec is counterproductive, and should be avoided. Python can't compile code in exec statements until execution, and won't be able to colour code your code.
People have been suggesting the use of python dictionaries, so I decided to research them. Dictionaries (dict) seem to be a data type similar to lists, except they can be indexed using strings (or other "immutable" data types). Here is a version of my first example that uses a dictionary instead of lists:
Objects={}
def createvtinstance(Object=4,Name="engine1"):
global Objects
Objects[Name]=Object
def Use(Name="engine1"):print(Objects[Name]) # Or: Objects[Name].SomeFunction()
Python seems to have a built in dictionary called globals, which stores all your variables, so you could probably do:
def createvtinstance(Object=4,Name="engine1"):
globals()[Name]=Object # Or globals()[Name]=vtdiagram()
However, this will allow the user to break your program, if they use a name like createvtinstance or tkinter.
This question already has answers here:
How to give column name dynamically from string variable in sql alchemy filter?
(4 answers)
Closed 5 years ago.
I've had this problem in the past and never found the solution. I've checked ton's of google links and still don't know.
What I want to do is use a string as a variable. I'm working with SQLalchemy so will use the example straight from my project: (look for the variable 'objective' in the function)
Here's an example:
def win_ratio_p_obj(objective):
#want to find the win/loss ratio for each obj_first, ie. 60% of times when team gets fblood you also win vs. 40% of time you lose
obj_totals = session.query(Match.win, func.count(Match.win)).filter(Match.**objective** == 't').group_by(Match.win).order_by(Match.win).all()
win_chance = obj_totals[1][1]/(obj_totals[0][1]+obj_totals[1][1])
return win_chance
objective = 'first_dragon'
x = win_ratio_p_obj(objective)
objective = 'first_blood'
y = win_ratio_p_obj(objective)
objective = 'first_turret'
z = win_ratio_p_obj(objective)
objective = 'first_inhib'
Returns:
Traceback (most recent call last):
Python Shell, prompt 15, line 1
builtins.AttributeError: type object 'Match' has no attribute 'objective'
So what I want to do is use each objective as a variable name with the aim of reducing code repetition. I know I could very easily copy paste the function a few times but that seems silly.
At the moment the code above won't recognise the objective variables values as variables instead of strings.
Any answers will be super well appreciated!
It seems like you could use getattr:
getattr(Match, objective)
This question already has answers here:
Python - Why is this class variable not defined in the method?
(3 answers)
Why is instance variable not getting recognized
(2 answers)
Closed 6 years ago.
I am writing a piece of code for a homework class, which should allow me to calculate various distance statistics about two lists. However, when I assign the lists to the class, and try to print the result of one of the functions, I get the error,
NameError: name 'ratings1' is not defined
Leading me to believe that I did something incorrectly either in my __init__ function or the referencing in the functions. Can you help clarify what I'm doing wrong?
class similarity:
def __init__(self, ratingX, ratingY):
self.ratings1=ratingX
self.ratings2=ratingY
def minkowski(self,r):
self.r=r
mink=0
length=len(ratings1)
for i in range(0,length):
mink=mink+(abs(ratings1[i]-ratings2[i]))**r
mink=mink**(1/r)
result='Given r=%d, Minkowski distance=%f'%(r,mink)
return result
def pearson(self):
Xavg=average(ratings1)
Yavg=average(ratings2)
n=len(ratings1)
diffX=[]
diffY=[]
for i in range(0,n):
diffX.append(ratings1[i]-Xavg)
diffY.append(ratings2[i]-Yavg)
return diffX
diffXY=[]
for i in range(0,n):
diffXY.append(diffX[i]*diffY[i])
example2=similarity([1,3,5,5,6],[4,6,10,12,13])
print(example2.pearson())
Note: this error persists if I change the references to "ratings1/2" to "ratingsX/Y" in the functions.
You need to use self before every reference to instance variable, ie self.ratings1, and your indentation is wrong as well.
ratings are associated with class. Use self.ratings1 and so on..
I just figured out my mistake. For each function I failed to use the self. phrase before the ratings name. To amend this, I added
ratings1=self.
ratings2=self.ratings2
To the beginning of each function. Problem solved.