These are the four built-in python methods for quickly accessing the attributes (properties) of object instances.
| Function | Parameter | Description |
|---|---|---|
| hasattr | (object, attr_name) | Returns a bool to tell you if the object has the attribute. |
| getattr | (object, attr_name, default_val) | Returns the value of the object attribute, or the default value if it does not exist. |
| setattr | (object, attr_name, val) | Set the value of the object attribute. Same as object.attr_name = val |
| delattr | (object, attr_name) | Delete the attribute of the object. Same as del object.attr_name |
class Cat:
def __init__(self):
self.age = 0
cat = Cat()
hasattr(cat, "age") # True
setattr(cat, "age", 10)
getattr(cat, "age", -1) # 10
delattr(cat, "age")
getattr(cat, "age", -1) # -1
cat.age # # AttributeError: 'Cat' object has no attribute 'age'This can be useful when you use list of dict to declare many instances.
class Cat:
...
listOfCats = []
attrs = [{"name": "meow1", "age": 5}, {"name": "meow2", "age": 10}]
for attr in attrs:
cat = Cat()
for key, val in attr.items():
setattr(cat, key, val)
listOfCats.append(cat)
cat1, cat2 = listOfCats
cat1.name # meow1
cat1.age # 5
cat2.name # meow2
cat2.age # 10| Article | Link |
|---|---|
| Using getattr, setattr, delattr, hasattr in Python | https://medium.com/@pranaygore/using-getattr-setattr-delattr-hasattr-in-python-6d79c6f9fda3 |
| Why use setattr() and getattr() built-ins? | https://stackoverflow.com/questions/19123707/why-use-setattr-and-getattr-built-ins |
| 10 Python Tips and Tricks For Writing Better Code | https://youtu.be/C-gEQdGVXbk?t=1511 |