CODEWITHSUNDEEP
pythonpython-3.xfunctiondel
Ronan Soares
Ronan Soares

Reputation: 23

Deleting an default argument inside function in Python

I have tried the following in the console:

>>> def f(l=[]):
...     l.append(1)
...     print(l)
...     del l
... 
>>> f()
[1]
>>> f()
[1, 1]

What I don't understand is how the interpreter is still able to find the same list l after the delete instruction. From the documentation l=[] should be evaluated only once.

Upvotes: 2

Views: 492

Answers (2)

Neo N3o
Neo N3o

Reputation: 86

To delete a element for the list,del l[:] should be used.If u use just l the list will remain itself.

def f(l=[]):
l.append(1)
print(l)
del l[:]
print(l)
>>> f()
[1]    #element in the list
[]     #list after deletion of the element
>>> f()
[1]
[]
>>> f()
[1]
[]

Upvotes: 0

khelwood
khelwood

Reputation: 59103

The variable is not the object. Each time the function is called, the local variable l is created and (if necessary) set to the default value.

The object [], which is the default value for l, is created when the function is defined, but the variable l is created each time the function runs.

Upvotes: 4

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