string-interpolation

问题 In Perl I can do something like the following: my $home = "/home"; my $alice = "$home/alice"; Can I do something like the following in YAML: Home: /home Alice: $Home/alice So "Alice" is effectively /home/alice in the end? 回答1: Unfortunately, you're out of luck. To do what you want you'd need to pass in $home from a view file (or wherever) and interpolate it in your yaml entry, which could possibly look something like: Alice: ! '%{home}/Alice' See this StackOverflow Q&A for the detailed answer

问题 Consider this fictitious Python function: def f(s): # accepts a string containing placeholders # returns an interpolated string return s % {'foo': 'OK', 'bar': 'OK'} How can I check that the string s provides all the expected placeholders, and if not, make the function politely show the missing keys? My solution follows. My question: is there a better solution? import sys def f(s): d = {} notfound = [] expected = ['foo', 'bar'] while True: try: s % d break except KeyError as e: key = e.args[0

问题 I am using template strings to generate some files and I love the conciseness of the new f-strings for this purpose, for reducing my previous template code from something like this: template_a = "The current name is {name}" names = ["foo", "bar"] for name in names: print (template_a.format(**locals())) Now I can do this, directly replacing variables: names = ["foo", "bar"] for name in names: print (f"The current name is {name}") However, sometimes it makes sense to have the template defined

问题 The official docs state: Both concatenation and string interpolation call string() to convert objects into string form However, the following minimum working example seems to demonstrate otherwise: type MyType x::Int end import Base.string Base.string(m::MyType) = "world" m = MyType(4) println("hello $m") println("hello " * string(m)) The second last line evaluates to hello MyType(4) at the REPL, while the last line evaluates (as expected) to hello world . So what am I doing wrong? (I am

问题 I am trying to bind classnames into the class attribute with vuejs looping through an array like this: Here I pass the method call in a :class="paymentTypeClass(value)" to bind to the vue template like so: <li v-for="card in paymentType" class="o-pf-list__item" :class="paymentTypeClass(value)"> {{ card }} </li> new Vue ({ el: '#app', data: { paymentType: ['paymentType1', 'paymentType2', 'paymentType3', 'paymentType4', 'paymentType5'] }, methods: { functionName: function(value) { var i = 0;

问题 The following code is an extract from rubykoans about_classes.rb: class Dog7 def initialize(initial_name) @name = initial_name end def to_s @name end end I created an instance of Dog7 : fido = Dog7.new("Fido") I understand the following: "My dog is " + fido.to_s # => "My dog is Fido" "My dog is #{fido.to_s}" # => "My dog is Fido" I do not understand why the following interpolation makes sense and gives the same result: "My dog is #{fido}" # => "My dog is Fido" fido is not a string. 回答1: The

问题 I have a long list of possible files I need to import. I will only ever need 1 of them and they all have the same interface. (Choosing a payment gateway to process a payment) Suppose I have a dictionary that represents the name of all the gateway files. i.e. gateways = { '1' : 'authorize', '2' : 'paysimple', '3' : 'braintreepayments', '4' : 'etc', } I know the keys to this dictionary based on information from a database. So, if I receive a payment process request with a gateway value of 1 I

问题 I tried to use string interpolation $"" in C#6 with tabs var name="My Name"; var text =$"\t\t{name}"; and it's working fine and tabs \t is resolved. When trying to use Long string interpolation lines var name = "myname"; var text = $@"\t\t{name} tab and name is in a Long string interpolation \r\n "; Console.WriteLine(text); output \t\tmyname tab and name is in a Long string interpolation \r\n The tab \t ,\r and \n aren't resolved So i had to use string.Format() to resolve this issue. The

问题 I have a PlayFramework server (with Anorm) which operates against a database with several schemas, all of them with the same tables. Most of my "access to database" functions look like: def findById(zoneName: String, id: Long): Option[Employee] = { DB.withConnection { implicit connection => SQL("""select * from """+zoneName+"""employee where employee._id = {id}""" .on( '_id -> id ).as(simpleParser.singleOpt) } } But I know this is a wrong approach, because it is not SQL-Injection-safe and of

问题 <?xml version="1.0" encoding="utf-8"?> <!-- Generator: Adobe Illustrator 18.1.1, SVG Export Plug-In . SVG Version: 6.00 Build 0) --> <svg version="1.1" id="Laag_1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px" viewBox="0 0 841.9 595.3" enable-background="new 0 0 841.9 595.3" xml:space="preserve"> <g> <defs> <pattern id="img1" patternUnits="userSpaceOnUse" width="600" height="450"> <image xlink:href="scheikunde havo4-344.jpg" x="0" y="0" width=