这个“for循环”如何通过对象的不同行进行索引

Question

学习 Python 3 the Hard Way 第 40 课的课程。我正在尽我最大的努力来理解这个“for循环”是如何计算的。

“对于 self.lyrics 中的行：打印（行）”

我还想知道如何将“行”转换为数字，以便可以在歌词行顶部打印行号。

我的轻微修改是添加另一行“你为什么脏老鼠”，看看它是否会按预期打印。我还删除了逗号，并按预期添加了该行

class Song():

    def __init__(self, lyrics):

        self.lyrics = lyrics

----------------------------------------------------

    def sing_me_a_song(self):

        for line in self.lyrics:

            print(line)

----------------------------------------------------

happy_bday = Song(["Happy birthday to you",

                   "I don't want to get sued ",

                   "Why you dirty rat",

                   "So ill stay right there"])

bulls_on_parade = Song(["They rally around tha family",

                        "With pockets full of shells"])

print("\n")

happy_bday.sing_me_a_song()

print("\n")

bulls_on_parade.sing_me_a_song()

print("\n")```

Answer 1

for i, line in enumerate(self.lyrics):     ...为您提供可迭代的索引和值。

Answer 2

我可以想到两种方法供您执行此操作。第一种方法是为“for”循环获取循环计数器。第二种方法是使用范围迭代列表或元组。方法一：class Song():    def __init__(self, lyrics):        self.lyrics = lyrics    def sing_me_a_song(self):        i = 0        for line in self.lyrics:            i = i + 1  # i here for first line 1 or after print for first line 0            print(str(i) + " : " + line)方法二：class Song():    def __init__(self, lyrics):        self.lyrics = lyrics    def sing_me_a_song(self):        for i in range(0,len(self.lyrics)):            print(str(i + 1) + " : " + self.lyrics[i]) # i + 1 to start at line 1 or just i to start at line 0