How to use a string as an already exist list function in python?-CodePudding

I want to use a string as an already exists list function. For example i got from a user as input: 'append'

How can i use this string as a function directly?

For example:

function_name = str(input(n)) # let say it is append
arr = []

arr.function_name(9)  #Of course it is not working because it is string. Not a function.

CodePudding user response：

Use getattr.

>>> a = []
>>> getattr(a, 'append')(1)
>>> a
[1]

That being said, it's not the best idea to execute arbitrary code based on user input. You should check the input against a collection of allowed methods first.

CodePudding user response：

All functions are attributes of the respective object. You can use the getattr function to get the function callable and then call it.

For Eg. ,

function_name = str(input("")) # let say it is append
arr = []

#Get the attribute and call it
# You can check if callable(function_to_call) to make sure its a function as well.
function_to_call = getattr(arr, function_name)
function_to_call(10)

print(arr)

CodePudding user response：

The method you are using is not possible.

But you can use this method instead...

function_name = str(input(n))
arr = []

if function_name == "append":
    arr.append(9)

or you can use getattr:

function_name = str(input(n))
arr = []

getattr(arr, fucntion_name)(9)