Facing the error as :
AttributeError: 'function' object has no attribute 'd'.
how to access the dictionary?
code:
class A:
#staticmethod
def test():
d = {}
d['a'] = 'b'
print d
#staticmethod
def test1():
d1 = {}
d1['a'] = 'c'
if (A.test.d['a'] == A.test1.d1['a']):
print "yes"
else:
print "Oh No!!"
A.test()
A.test1()
Check out this on the matter of static variables in Python.
You should be able to sort it out using A.d and A.d1 whenever you wish to use the static variables. Note that, as you have them, they are local to test and test1, respectively. If you want them to be static, you have to declare them inside the class scope, but not within any function definition.
Related
I am a beginner in Python and I am trying to understand trees better. Why can't I add nodes inside the function f below? I would expect that the final print returns the value 2 instead of an error that f(test) in None.
class Testcls(object):
def __init__(self,data):
self.data= data
self.children = []
def add_child(self,obj):
self.children.append(obj)
def f(test):
data1 = test.data+1
test.add_child(Testcls(data1))
test = Testcls(1)
print f(test).data
Final print in your case should actually return an error. Function f doesn't return anything (hence the None if you type print f(test). To add children using f you can add a return statement:
def f(test):
data1 = test.data+1
test.add_child(Testcls(data1))
return test
Which now returns the object test which you can further access and process,
f(test)
print test.children[0].data
Since it actually returns the test object you can also call it and use it directly:
print (f(test).children)[0].data
You don't have to have a return statement either - f will still change the object you're sending to it. In case you don't want to return the object, you just need to call the function separately and only then use test like shown in the second code snippet.
I have an enum like this
#enum.unique
class TransactionTypes(enum.IntEnum):
authorisation = 1
balance_adjustment = 2
chargeback = 3
auth_reversal = 4
Now i am assigning a variable with this enum like this
a = TransactionTypes
I want to check for the type of 'a' and do something if its an enum and something else, if its not an enum
I tried something like this
if type(a) == enum:
print "do enum related stuff"
else:
print "do something else"
The problem is it is not working fine.
Now i am assigning a variable with this enum like this
a = TransactionTypes
I hope you aren't, because what you just assigned to a is the entire enumeration, not one of its members (such as TransactionTypes.chargeback) If that is really what you wanted to do, then the correct test would be:
if issubclass(a, enum.Enum)
However, if you actually meant something like:
a = TransactionTypes.authorisation
then the test you need is:
# for any Enum member
if isinstance(a, Enum):
or
# for a TransactionTypes Enum
if isinstance(a, TransactionTypes):
reliable solution:
from enum import IntEnum
from collections import Iterable
def is_IntEnum(obj):
try:
return isinstance(obj, Iterable) and isinstance (next(iter(obj)), IntEnum)
except:
return False # Handle StopIteration, if obj has no elements
I thought I`ve got a ugly way. eg:
print(o.__class__.__class__)
Output:
<enum.EnumMeta>
as mentioned use isinstance method to check weather an instance is of enum.Enum type or not.
A small working code for demonstration of its usage:
import enum
class STATUS(enum.Enum):
FINISHED = enum.auto()
DELETED = enum.auto()
CANCELLED = enum.auto()
PENDING = enum.auto()
if __name__ == "__main__":
instance = STATUS.CANCELLED
if isinstance(instance, enum.Enum):
print('name : ', instance.name, ' value : ', instance.value)
else:
print(str(instance))
Output:
name : CANCELLED value : 3
There are already good answers here but in case of it might be useful for some people out there
I wanted to stretch the question a little further and created a simple example
to propose a humble solution to help caller function who does maybe little knowledge about Enum
solve problem of sending arguments to functions that take only Enum
as a parameter by proposing a converter just below the file that Enum was created.
from enum import Enum
from typing import Union
class Polygon(Enum):
triangle: 3
quadrilateral: 4
pentagon: 5
hexagon: 6
heptagon: 7
octagon: 8
nonagon: 9
decagon: 10
def display(polygon: Polygon):
print(f"{polygon.name} : {polygon.value} ")
def do_something_with_polygon(polygon: Polygon):
"""This one is not flexible cause it only accepts a Polygon Enum it does not convert"""
""" if parameter is really a Polygon Enum we are ready to do stuff or We get error """
display(polygon)
def do_something_with_polygon_more_flexible(maybe_polygon_maybe_not: Union[Polygon, int, str]):
""" it will be more convenient function by taking extra parameters and converting"""
if isinstance(maybe_polygon_maybe_not, Enum):
real_polygon = maybe_polygon_maybe_not
else:
real_polygon = get_enum_with_value(int(maybe_polygon_maybe_not), Polygon, Polygon.quadrilateral)
""" now we are ready to do stuff """
display(real_polygon)
def get_enum_with_value(key: int, enum_: any, default_value: Enum):
""" this function will convert int value to Enum that corresponds checking parameter key """
# create a dict with all values and name of Enum
dict_temp = {x.value: x for x in
enum_} # { 3 : Polygon.triangle , 4 :Polygon.quadrilateral , 5 : Polygon.pentagon , ... }
# if key exists for example 6 or '6' that comes to do_something_with_polygon_more_flexible
# returns Polygon.hexagon
enum_value = dict_temp.get(key, None)
# if key does not exist we get None
if not enum_value:
... # if key does not exist we return default value (Polygon.quadrilateral)
enum_value = default_value # Polygon.quadrilateral
return enum_value
How come the length Current_Stock.open can be greater than 0 if I just created the instance of the class?
def initialize_stock(row):
Current_Stock=Stock()
print len(Current_Stock.open)
do some stuff than return object
Loop that calls initializer
for row in xrange(1,sheet.nrows,25):
New_Stock= Stock() #create new instance of class
New_Stock= initialize_stock(row)
stocks.append(New_Stock) #add instance to stocks array
Stock class
class Stock:
name=''
date=[]
open=[]
high=[]
low=[]
close=[]
percent_change_price=[]
percent_change_volume= []
The reason is, that your attributes are not instance variables, but class attributes.
You declared them on class level -- and in Python this means, that they are class attributes by default.
Only variables that are created inside methods are instance variables and also they must be always used with "self." prefix, e.g.:
def __init__(self):
...
self.open = []
...
I'm getting this error:
unbound method hello() must be called with A instance as first argument(got nothing instead)
import B
class A():
#staticmethod
def newHello():
A.oldHello() # Here the error
print ' world'
def inject(self):
A.oldHello = B.hello
B.hello = A.newHello
A().inject()
B.hello()
B.py contain only a function "hello" that print "hello"
def hello():
print 'hello'
Thanks in advance
A.oldhello() is not static. So in B's hello function is referencing A's nonstatic oldhello statically. A does in fact need an instance. I'm not too good with the decorators and how they work but maybe try declaring oldhello in the class before the function and calling it #staticmethod. I don't know if the staticness carries over if you override the method.
Try this:
class B():
def hello(self):
print "hello"
class A():
#staticmethod
def newHello(self):
A.oldHello(self) # Here the error
print ' world'
def inject(self):
A.oldHello = B.hello
B.hello = A.newHello
A().inject()
B().hello()
Possible duplicates:
Is there a way to create subclasses on-the-fly?
Dynamically creating classes - Python
I would like to create a subclass where the only difference is some class variable, but I would like everything else to stay the same. I need to do this dynamically, because I only know the class variable value at run time.
Here is some example code so far. I would like FooBase.foo_var to be "default" but FooBar.foo_var to be "bar." No attempt so far has been successful.
class FooBase(object):
foo_var = "default"
def __init__(self, name="anon"):
self.name = name
def speak(self):
print self.name, "reporting for duty"
print "my foovar is '" + FooBase.foo_var + "'"
if __name__ == "__main__":
#FooBase.foo_var = "foo"
f = FooBase()
f.speak()
foobarname = "bar"
#FooBar = type("FooBar", (FooBase,), {'foo_var': "bar"})
class FooBar(FooBase): pass
FooBar.foo_var = "bar"
fb = FooBar()
fb.speak()
Many thanks
EDIT so I obviously have a problem with this line:
print "my foovar is '" + FooBase.foo_var + "'"
The accepted answer has self.foo_var in the code. That's what I should be doing. I feel ridiculous now.
What about this:
def make_class(value):
class Foo(object):
foo_var = value
def speak(self):
print self.foo_var
return Foo
FooBar = make_class("bar")
FooQux = make_class("qux")
FooBar().speak()
FooQux().speak()
That said, can't you make the value of foo_var be a instance variable of your class? So that the same class instantiated with different input behaves in different ways, instead of creating a different class for each of those different behaviours.