int accepts x as a keyword argument in Python 2

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The following works in Python 2.7:

In [79]: int(x=5)
Out[79]: 5

.. but fails in Python 3.6:

In [31]: int(x=5)
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-31-53a6d75bfa9f> in <module>
----> 1 int(x=5)

TypeError: 'x' is an invalid keyword argument for int()

Seems like the behavior was corrected in Python 3 to not accept x as a keyword argument. Can someone please confirm that my understanding is right or else correct me? Thanks.

According to Python2 docs: https://docs.python.org/2/library/functions.html#int

The int signature is class int(x=0) or class int(x, base=10) which supports assigments as you observed in case of `int(x=5)

According to Python3 docs: https://docs.python.org/3/library/functions.html#int

The int signature is class int([x]) or class int(x, base=10) where x is a variable assigned outside the function parameter, like int('5')

Glossary — Python 2.7.18 documentation, A tool that tries to convert Python 2.x code to Python 3.x code by positional argument: an argument that is not a keyword argument. For example, int(3.15) converts the floating point number to the integer A number of tools in Python accept key functions to control how elements are ordered or grouped. There’s no syntactic way in Python 2 to require an argument to be named. Keyword-only arguments without positional arguments. What if you want to accept keyword-only arguments without also accepting unlimited positional arguments? If you want to accept keyword-only arguments and you’re not using a * to accept any number of positional

In Python 2, the signature of int() is

int(x=0)
int(x, base=10)

In Python 3, it is nearly identical:

int([x])
int(x, base=10)

But in Python 2 it was not possible to disallow keyword arguments. In Python 3 it is.

4. More Control Flow Tools — Python 2.7.18 documentation, x = int(raw_input("Please enter an integer: ")) Please enter an integer: 42 > The keyword ' elif ' is short for 'else if', and is useful to avoid excessive indentation. accepts one required argument ( voltage ) and three optional� This generates a string similar to that returned by repr() in Python 2. bin(x)¶ Convert an integer number to a binary string. The result is a valid Python expression. If x is not a Python int object, it has to define an __index__() method that returns an integer. class bool([x])¶ Return a Boolean value, i.e. one of True or False.

Yes , the signature changed. You can compare the docs.

Python 3.x shows this signature

class int([x])
class int(x, base=10)

But Python 2.x shows this:

class int(x=0)
class int(x, base=10)

Notice how 3.x does not accept keyword argument, but 2.x does.

PEP 612 -- Parameter Specification Variables, When one defines a function (like inner) that takes (*args, **kwargs) and return x + 7 takes_int_str(1, "A") takes_int_str("B", 2) # fails at runtime Furthermore, because the default kind of parameter in Python ((x: int)) may be� Python allows functions to be called using keyword arguments. When we call functions in this way, the order (position) of the arguments can be changed. Following calls to the above function are all valid and produce the same result.

In pythong 3.6 you should separate with a comma. The syntax of int() method is: int(x=0, base=10)

You can see more in the documentation here: https://www.programiz.com/python-programming/methods/built-in/int

Parsing arguments and building values — Python 3.8.5 documentation, the type of the length argument (int or Py_ssize_t ) is controlled by defining the If you want to accept filesystem paths and convert them to C character strings, it is An exception is raised if the named encoding is not known to Python. NULL; PyObject *result = NULL; if (PyArg_UnpackTuple(args, "ref", 1, 2, &object,� The special syntax **kwargs in function definitions in python is used to pass a keyworded, variable-length argument list. We use the name kwargs with the double star. The reason is because the double star allows us to pass through keyword arguments (and any number of them).

2. Built-in Functions — Python 2.7.18 documentation, If x is not a Python int object, it has to define an __index__() method that returns The function deletes the named attribute, provided the object allows it. Changed in version 2.3: This function does not accept any arguments. You can easily pass command line arguments to a Python script. In this tutorial, we will help you to read the command line arguments in a Python script. Below is the sample Python script, which reads the command line arguments and print details. Create a sample script like script.py and copy below content.

Action objects are used by an ArgumentParser to represent the information needed to parse a single argument from one or more strings from the command line. The Action class must accept the two positional arguments plus any keyword arguments passed to ArgumentParser.add_argument() except for the action itself.

Python 3’s sorted() does not have a cmp parameter. Instead, only key is used to introduce custom sorting logic. key and reverse must be passed as keyword arguments, unlike in Python 2, where they could be passed as positional arguments. If you need to convert a Python 2 cmp function to a key function, then check out functools.cmp_to_key

Comments
  • int in python 3 expects only two non-keyworded arguments, which is the string and the base
  • According to the docs, it should only fail in Python 3.7+ ("Changed in version 3.7: x is now a positional-only parameter."). I testet it on repl.it with Python 3.6.1 and it does not throw an error. But this might be an implementation detail of your ipython installation.