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I have the following code snippet:
from time import time
class Transaction:
def __init__(self, value, timestamp=time()):
self.value = value
self.created_at = timestamp
Creating an instance and seeing your timestamp:
t1 = Transaction()
t1.created_at
'1554492682.907307'
Now creating a second instance and also seeing your timestamp:
t2 = Transaction()
t2.created_at
'1554492682.907307'
Note that the timestamp of the object t2 is the same as the object of the object t1 and were not created at the same time logically.
Why the argument that has a default value is being calculated only once and repeating for all subsequent objects?
Same old scheme: any doubt just ask. If you disagree that it is duplicated let me know that we reevaluate the closure.
– Woss
@Andersoncarloswoss In the answer you have marked it says that this behavior occurs for only mutable types like "dictionaries, lists, etc". In my doubt, the created_at attribute is float type, but float is not immutable?
– Thiago Krempser
The idea is: the default value of the argument is defined at the time of class definition, that is, its function time will be called only once and will use the return as default value.
– Woss