What's the meaning of '@' in python code?

Question

Reading some Python (PyQt) code, I came across as follows.

@pyqtSignature("QString")
def on_findLineEdit_textEdited(self, text):
    self.__index = 0
    self.updateUi()

How does this @pyqtSignature work? How Python treat this @?

Answer 1

It is a syntax for function decorators.

Answer 2

It is the decorator syntax, simply it is equivalent to this form:

on_findLineEdit_textEdited = pyqtSignature("Qstring")(on_findLineEdit_textEdited)

Really simple.

A typical decorator takes as the first argument the function that has to be decorated, and perform stuff/adds functionalities to it. A typical example would be:

def echo_fname(f):
    def newfun():
       print f.__name__
       f()
    return newfun

The steps are:

• define a new function that add functionalities to f
• return this new function.