CODEWITHSUNDEEP
pythonclassvariables
Hanfei Sun
Hanfei Sun

Reputation: 47101

how to access the class variable by string in Python?

The codes are like this:

class Test:
    a = 1
    def __init__(self):
        self.b=2

When I make an instance of Test, I can access its instance variable b like this(using the string "b"):

test = Test()
a_string = "b"
print test.__dict__[a_string]

But it doesn't work for a as self.__dict__ doesn't contain a key named a. Then how can I accessa if I only have a string a?

Thanks!

Upvotes: 38

Views: 42924

Answers (5)

kindall
kindall

Reputation: 184455

To get the variable, you can do:

getattr(test, a_string)

Upvotes: 69

Ishan Ojha
Ishan Ojha

Reputation: 400

Since the variable is a class variable one can use the below code:-

class Test:
    a = 1
    def __init__(self):
        self.b=2

print Test.__dict__["a"]

Upvotes: 1

Miquel Santasusana
Miquel Santasusana

Reputation: 73

You can use:

getattr(Test, a_string, default_value)

with a third argument to return some default_value in case a_string is not found on Test class.

Upvotes: 6

Mark
Mark

Reputation: 6404

Try this:

class Test:    
    a = 1    
    def __init__(self):  
         self.b=2   

test = Test()      
a_string = "b"   
print test.__dict__[a_string]   
print test.__class__.__dict__["a"]

Upvotes: 7

Artsiom Rudzenka
Artsiom Rudzenka

Reputation: 29131

use getattr this way to do what you want:

test = Test()
a_string = "b"
print getattr(test, a_string)

Upvotes: 14

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