带有可选参数的Varargs函数

如何解决带有可选参数的Varargs函数

我有一个脚本import turtle import math import random import time screen = turtle.Screen() screen.title("Shape Shop") screen.setup(width=500,height=700) screen.bgcolor('lightsteelblue') turtleS = turtle.Turtle() turtleS.ht() turtleS.penup() turtleS.goto(0,250) turtleS.write("Welcome to the Shape Shop",align="center",font=("Avenir",18,"bold","underline")) pen = turtle.Turtle() pen.pensize(2) pen.ht() def instructions(): instPen = turtle.Turtle() instPen.ht() instPen.penup() instPen.goto(0,205) instPen.pendown() instPen.write("For this game,you can:",12)) instPen.penup() instPen.goto(-120,170) instPen.pendown() instPen.write("• Type in the name of a shape",12)) instPen.penup() instPen.goto(-100,145) instPen.pendown() instPen.write("- Names must be in lowercase",120) instPen.pendown() instPen.write("- Shape must have 12 or less sides",95) instPen.pendown() instPen.write("• Type in a number of sides",70) instPen.pendown() instPen.write("- Number must be less than 25",35) instPen.pendown() instPen.write(": The program will then draw the shape",10) instPen.pendown() instPen.write(": And tell you what shape it is",12)) instPen.penup() instPen.goto(-240,-340) instPen.pendown() instPen.write("Shape Shop v1.0",8)) instructions() def regShapeDraw(): length = ((1 / sides) * 500) angle = (360 / sides) pen.forward(length / 2) for i in range(sides - 1): pen.left(angle) pen.forward(length) pen.left(angle) pen.forward(length / 2) sides = [] def startUp(): mainGame() screen.listen() screen.onkeypress(startUp,"d") def mainGame(): userInput = screen.textinput("What shape do you want? ","Enter a shape name or a number of sides: ") if userInput == "COOL": eggPen = turtle.Turtle() eggPen.speed(0) eggPen.color('black') eggPen.penup() eggPen.goto(0,-80) eggPen.pendown() rotate=int(360) def drawCircles(t,size): size = 70 for i in range(5): t.circle(size) size=size-4 def drawSpecial(t,size,repeat): for i in range (repeat): drawCircles(t,size) t.right(360/repeat) drawSpecial(eggPen,100,10) shapeName = "WOAH!" else: if userInput.isalpha(): if userInput == "triangle": pen.penup() pen.goto(0,-300) pen.pendown() sides = 3 regShapeDraw() elif userInput == "square": pen.penup() pen.goto(0,-300) pen.pendown() sides = 4 regShapeDraw() elif userInput == "quadrilateral": pen.penup() pen.goto(0,-300) pen.pendown() sides = 4 regShapeDraw() elif userInput == "pentagon": pen.penup() pen.goto(0,-300) pen.pendown() sides = 5 regShapeDraw() elif userInput == "hexagon": pen.penup() pen.goto(0,-300) pen.pendown() sides = 6 regShapeDraw() elif userInput == "septagon": pen.penup() pen.goto(0,-300) pen.pendown() sides = 7 regShapeDraw() elif userInput == "heptagon": pen.penup() pen.goto(0,-300) pen.pendown() sides = 7 regShapeDraw() elif userInput == "octagon": pen.penup() pen.goto(0,-300) pen.pendown() sides = 8 regShapeDraw() elif userInput == "nonagon": pen.penup() pen.goto(0,-300) pen.pendown() sides = 9 regShapeDraw() elif userInput == "decagon": pen.penup() pen.goto(0,-300) pen.pendown() sides = 10 regShapeDraw() elif userInput == "hendecagon": pen.penup() pen.goto(0,-300) pen.pendown() sides = 11 regShapeDraw() elif userInput == "dodecagon": pen.penup() pen.goto(0,-300) pen.pendown() sides = 12 regShapeDraw() else: pen.penup() pen.goto(0,-250) pen.pendown() pen.write("We don't seem to have that shape in our database. You could try:",font=("Arial",12)) pen.penup() pen.goto(0,-275) pen.pendown() pen.write("» Making all the letters lowercase",-300) pen.pendown() pen.write("» Checking your spelling",-325) pen.pendown() pen.write("» Making sure the shape you want has 12 or less sides",12)) elif userInput.isnumeric(): if int(userInput) <= 25: pen.penup() pen.goto(0,-300) pen.pendown() sides = int(userInput) regShapeDraw() else: pen.penup() pen.goto(0,-250) pen.pendown() pen.write("We don't seem to have that shape in our database. You could try:",12)) pen.penup() pen.goto(0,-275) pen.pendown() pen.write("» Making the number less than 25",12)) else: pen.penup() pen.goto(0,-275) pen.pendown() pen.write("» Making your input all letters or all numbers",12)) if userInput == "3": shapeName = "Triangle" elif userInput == "4": shapeName = "Square" elif userInput == "5": shapeName = "Pentagon" elif userInput == "6": shapeName = "Hexagon" elif userInput == "7": shapeName = "Heptagon" elif userInput == "8": shapeName = "Octagon" elif userInput == "9": shapeName = "Nonagon" elif userInput == "10": shapeName = "Decagon" elif userInput == "11": shapeName = "Hendecagon" elif userInput == "12": shapeName = "Dodecagon" elif userInput == "13": shapeName = "Triskaidecagon" elif userInput == "14": shapeName = "Tetrakaidecagon" elif userInput == "15": shapeName = "Pentadecagon" elif userInput == "16": shapeName = "Hexakaidecagon" elif userInput == "17": shapeName = "Heptadecagon" elif userInput == "18": shapeName = "Octakaidecagon" elif userInput == "19": shapeName = "Enneadecagon" elif userInput == "20": shapeName = "Icosagon" elif userInput == "21": shapeName = "Icosikaihenagon" elif userInput == "22": shapeName = "Icosikaidigon" elif userInput == "23": shapeName = "Icosikaitrigon" elif userInput == "24": shapeName = "Icositetragon" elif userInput == "25": shapeName = "Icosikaipentagon" elif userInput == "triangle": shapeName = "Triangle" elif userInput == "square": shapeName = "Square" elif userInput == "quadrilateral": shapeName = "Square" elif userInput == "pentagon": shapeName = "Pentagon" elif userInput == "hexagon": shapeName = "Hexagon" elif userInput == "heptagon": shapeName = "Heptagon" elif userInput == "septagon": shapeName = "Heptagon" elif userInput == "octagon": shapeName = "Octagon" elif userInput == "nonagon": shapeName = "Nonagon" elif userInput == "decagon": shapeName = "Decagon" elif userInput == "hendecagon": shapeName = "Hendecagon" elif userInput == "dodecagon": shapeName = "Dodecagon" else: shapeName = "¯\(°_o)/¯" typeName = turtle.Turtle() typeName.ht() typeName.penup() typeName.goto(0,-120) typeName.pendown() typeName.write(shapeName,30,"bold")) screen.mainloop() ，其功能可以带4个参数，其中2个是可选的。我可以轻松地做到这一点

foo.jl

我可以使用终端中的参数调用

function bar(a,b,c=1,d=2)
    println(a,c,d)
end

bar(ARGS[1],ARGS[2],ARGS[3],ARGS[4])

但是，如果我只想用$:> julia foo.jl 1 2 3 4 1234 和a指定前两个参数b和c=1，那么我将无法使用d=2，因为脚本不包含带有2个参数的函数调用。解决方法是测量$:> julia foo.jl 1 2中ARGS的长度并有条件地调用foo.jl：

bar

但是，当超出4个参数时，这有点笨重。所以我研究了使用可变参数，在这里我可以用

调用任意数量的参数

if length(ARGS) == 2
    bar(ARGS[1],ARGS[2])
elseif length(ARGS) == 3
    bar(ARGS[1],ARGS[3])
else
    bar(ARGS[1],ARGS[4])
end

以多种方式调用

function bar(a,x...)
    println(a,x)
end

bar(ARGS[1],ARGS[3:end])

但是，如果终端中未提供$:> julia foo.jl 1 2 12(String[],) $:> julia foo.jl 1 2 3 4 12(["3","4"],) $:> julia foo.jl 1 2 3 4 5 6 12(["3","4","5","6"],) 的默认设置，我不知道如何（或者是否能够）设置。像x...这样的幼稚内容不起作用。此处的解决方案是根据function bar(a,x...=(1,2))的内容或大小在函数内设置变量。但我不知道是否有更好的方法可以做到这一点。

因此，我正在寻找一种使用终端中的参数调用函数的方法，其中需要一个数字（在这种情况下为2），而其余数字是可选的并设置为默认值。

解决方法

也许您正在寻找以下功能：

function flexiargs(a1,a2,a3="3",a4="4",a5="5",a6...)
    println((a1,a3,a4,a5,a6))
end
flexiargs(args::AbstractVector)=flexiargs(args...)

此函数将与任意数量的参数一起使用，前提是它们中至少有两个。

让我们测试以下数据：

args0=["one","two"]
args1=["one","two","three","four"];
args2=vcat(args,"five","six","seven") 

让我们看看它是如何工作的：

julia> flexiargs(args0)
("one","3","4","5",())

julia> flexiargs(args1)
("one","four",())

julia> flexiargs(args2)
("one",("six","seven"))

最后请注意，这也是可以的：

function flexiargs(a1,a6...=("6","7"))
    println((a1,a6))
end
flexiargs(args::AbstractVector)=flexiargs(args...)

在这种情况下，默认情况下（如果args中没有足够的值）a6将只是一个元素Tuple，而唯一的元素是Tuple {{ 1}}。