英文:
Why must my code include line = '' + '-' instead of line = '-'
问题
代码1输出：
World
-----
代码2输出：
World
-
为什么代码2没有与代码1相同的输出？
我真的不明白。
英文:
CODE 1
name = 'World'
line = ''
for char in name:
line = line + '-'
print(name)
print(line)
Versus
CODE 2
name = 'World'
line = ''
for char in name:
line = '-'
print(name)
print(line)
Why doesn't code 2 have the output
World
-----
as well? I really don't get it
答案1
得分: 3
只要考虑这实际意味着的是：
for char in name:
line = '-'
for 关键字告诉解释器遍历name中的所有字符。对于World中的每个字符，它将运行一次line = '-'。
第一次执行line = '-'时，变量line被设置为'-'。
但第二次和第三次也是如此。
这是两个程序之间的区别。在第一个程序中，你执行line = line + '-'。你取当前的line并在末尾添加一个额外的'-'。
英文:
Just think about what this actually means:
for char in name:
line = '-'
The for keyword tells the interpreter to iterate over all characters in name. It will run line = '-' once for every character in World.
The first time line = '-' get's executed, the variable line gets set to '-'.
But so does it the second time. And the third time.
That's the difference between the two programs. In the first program you do line = line + '-'. You take the current line and add a further '-' at the end
答案2
得分: 1
问题在于循环中的那一行没有聚合“-”字符。
要解决这个问题，你有两个选项：
- 像你在你的第一段代码中所做的那样。
for char in name:
line = line + '-'
- 也可以这样。
for char in name:
line += '-'
英文:
The problem you have is that line in loop is not aggragating the - char.
For doing so you have two options:
- Like you did in your first code.
for char in name:
line = line + '-'
- Like this.
for char in name:
line += '-'
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