The example explains how to call and define functions in Python, and the example explains python

The example explains how to call and define functions in Python, and the example explains python

Call the function:

#! /Usr/bin/env python3 #-*-coding: UTF-8-*-# function call >>> abs (100) 100 >>> abs (-110) 110 >>> abs (12.34) 12.34 >>> abs (1, 2) Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: abs () takes exactly one argument (2 given)> abs ('A') Traceback (most recent call last ): file "<stdin>", line 1, in <module> TypeError: bad operand type for abs (): 'str' >>> max (1, 2) 2 >>> max (2, 3, 1,-5) 3 >>> int ('000000') 123 >>> int (123) 12 >>> str (1.23) '1. 23' >>> str (100) '20140901' >>> bool (1) True >>> bool ('') false >>> a = abs # variable a points to the abs function, which is equivalent to referencing >>> a (-1) # therefore, you can call abs function 1> n1 = 255> n2 = 1000> print (hex (n1 )) 0xff >>> print (hex (n2) 0x3e8

Define functions:

#! /Usr/bin/env python3 #-*-coding: UTF-8-*-# Function Definition def myAbs (x): if x> = 0: return x else: return-x a = 10 myAbs (a) def nop (): # null Function pass

The pass statement does not do anything.
In fact, pass can be used as a placeholder. For example, if you haven't thought about how to write the function code, you can first write a pass to run the code.

If age> = 18: pass # The Code has a syntax error if pass # Is Missing >>> if age> = 18 :... file "<stdin>", line 2 ^ IndentationError: expected an indented block >>> myAbs (1, 2) Traceback (most recent call last): File "<stdin> ", line 1, in <module> TypeError: myAbs () takes 1 positional argument but 2 were given> myAbs ('A') Traceback (most recent call last ): file "<stdin>", line 1, in <module> File "<stdin>", line 2, in myAbs TypeError: unorderable types: str ()> = int () >>> abs ('A') Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: bad operand type for abs (): 'str' def myAbs (x): if not isinstance (x, (int, float): raise TypeError ('bad operand type ') if x> = 0: return x else: return-x> myAbs ('A') Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<stdin>", line 3, in myAbs TypeError: bad operand type

Return two values?

import math def move(x, y, step, angle = 0):  nx = x + step * math.cos(angle)  ny = y - step * math.sin(angle)  return nx, ny  >>> x, y = move(100, 100, 60, math.pi / 6) >>> print(x, y) 151.96152422706632 70.0 

In fact, the above is just an illusion that the Python function returns a single value.

>>> r = move(100, 100, 60, math.pi / 6) >>> print(r) (151.96152422706632, 70.0) 

Actually, a tuple is returned!
However, in syntax, a tuple can be returned without parentheses, while multiple variables can accept a tuple at the same time and assign the corresponding value by position.
Therefore, the Python function returns a tuple, but it is easier to write.
If no return statement is returned after the function is executed, the return None statement is automatically returned.

Exercise:

import math def quadratic(a, b, c):  x1 = (-b + math.sqrt(b * b - 4 * a * c)) / (2 * a)  x2 = (-b - math.sqrt(b * b - 4 * a * c)) / (2 * a)  return x1, x2  x1, x2 = quadratic(2, 5, 1) print(x1, x2)  >>> import math >>> def quadratic(a, b, c): ...  x1 = (-b + math.sqrt(b * b - 4 * a * c)) / (2 * a) ...  x2 = (-b - math.sqrt(b * b - 4 * a * c)) / (2 * a) ...  return x1, x2 ... >>> x1, x2 = quadratic(2, 5, 1) >>> print(x1, x2) -0.21922359359558485 -2.2807764064044154

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