Python Importing Class Attributes Into Method Local Namespace
Solution 1:
Q. Is there any way to do this more compact way?
1. If the variables are read-only, it would be reasonably Pythonic to factor-out a multi-variable accessor method:
classTest:
def__init__(self):
self.a = 10
self.b = 20
self.c = 30def_read_vars(self):
return self.a, self.b, self.c
defdosomething(self):
a, b, c = self._read_vars()
return a + b * c
defdosomethingelse(self):
a, b, c = self._read_vars()
return a - b * c
If the variables aren't read-only, it is best to stick with self.inst_var = value
. That is the normal way to write Python code and is usually what most people expect.
2. Once in a while you will see people abbreviate self
with a shorter variable name. It is used when the readability benefits of decluttering outweigh the readability cost of using a non-standard variable name:
def updatesomethings(s):
s.a, s.b, s.c = s.a + s.c, s.b - s.a, s.c * s.b
3. Another way to handle a very large number instance variable is to store them in a mutable container for ease of packing and unpacking:
classTest:
def__init__(self, a, b, c, d, e, f, g, h, i):
self._vars = [a, b, c, d, e, f, g, h, i]
deffancy_stuff(self):
a, b, c, d, e, f, g, h, i = self._vars
a += d * h - g
b -= e * f - c
g = a + b - i
self._vars[:] = a, b, c, d, e, f, g, h, i
4. There is also a dictionary manipulation approach that would work, but it has a code smell that most Pythonistas would avoid:
defupdatesomethings(self):
a = 100
b = 200
c = 300vars(self).update(locals())
del self.self
Solution 2:
You can easily solve this problem with a tradeoff, by storing the variables in a dictionary.
data = {}
copy_to_local_variables = ["a", "b", "c", "d"]
for var_name in copy_to_local_variables:
data[var_name] = getattr(self, var_name)
(Though I am unable to understand why you need to copy class attributes to method local namespace)
Solution 3:
I found another way:
defdosomething(self):
for key in ['a', 'b']:
exec('{} = self.{}'.format(key, key))
return(a + b)
I don't know if this is dangerous or not. Would be great if someone can comment on this.
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