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python - 这个 for 循环有什么作用？- 乐谱

问题描述

下面是完整的代码，它从字典中获取书面字符并将其转换为乐谱。我想知道是否有人可以向我解释 for 循环是如何工作的。

char2notes = { 
  ' ':("a4 a4 ", "r2 "),
  'a':("<c a>2 ", "<e' a'>2 "),
  'b':("e2 ", "e'4 <e' g'> "),
  'c':("g2 ", "d'4 e' "), 
  'd':("e2 ", "e'4 a' "),
  'e':("<c g>2 ", "a'4 <a' c'> "),
  'f':("a2 ", "<g' a'>4 c'' "),
  'g':("a2 ", "<g' a'>4 a' "),
  'h':("r4 g ", " r4 g' "),
  'i':("<c e>2 ", "d'4 g' "),
  'j':("a4 a ", "g'4 g' "),
  'k':("a2 ", "<g' a'>4 g' "),
  'l':("e4 g ", "a'4 a' "),
  'm':("c4 e ", "a'4 g' "),
  'n':("e4 c ", "a'4 g' "),
  'o':("<c a g>2  ", "a'2 "),
  'p':("a2 ", "e'4 <e' g'> "),
  'q':("a2 ", "a'4 a' "),
  'r':("g4 e ", "a'4 a' "),
  's':("a2 ", "g'4 a' "),
  't':("g2 ", "e'4 c' "),
  'u':("<c e g>2  ", "<a' g'>2"),
  'v':("e4 e ", "a'4 c' "),
  'w':("e4 a ", "a'4 c' "),
  'x':("r4 <c d> ", "g' a' "),
  'y':("<c g>2  ", "<a' g'>2"),
  'z':("<e a>2 ", "g'4 a' "),
  '\n':("r1 r1 ", "r1 r1 "),
  ',':("r2 ", "r2"),
  '.':("<c e a>2 ", "<a c' e'>2")
}

txt = "Love one another and you will be happy. It is as simple as that."

upper_staff = ""
lower_staff = "" 
for i in txt.lower():
    (l,u) = char2notes[i]
    upper_staff += u
    lower_staff += l

staff = "{\n\\new PianoStaff << \n"
staff += "  \\new Staff {" + upper_staff + "}\n"  
staff += "  \\new Staff { \clef bass " + lower_staff + "}\n"  
staff += ">>\n}\n"

title = """\header {
  title = "Love One Another"
  composer = "Bernd Klein using Python"
  tagline = "Copyright: Bernd Klein"
}"""

print (title + staff)

标签： pythonpython-3.xdictionary

解决方案

字符串实际上只是字符列表，因此您的 for 循环遍历字符串中的每个字符，找到对应于该字符的元组（或者如果它是大写，则该字符的小写等效项），将元组中的第一个元素附加到您的 lower_staff 字符串使用 += 运算符，对第二个元素和 upper_staff 执行相同的操作。

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