Python的范围函数是如何工作的？ [英] How does the Python's range function work?

问题描述

所有我在以下的循环中都不是很了解，谁能提供一些提示？提前致谢

  for我在范围（5）：
打印我
  

然后它给0,1,2 3,4是python把0,1,2,3,4同时分配给我的？但是如果我写道：

 我在范围（5）中：
a = i + 1 
  

然后我调用一个，它只给出5，但是如果我添加''打印一个''它给1,2， 3,4,5。所以我的问题是这里有什么区别？我是一个字符串或列表或别的东西？或者任何人都可以帮我理清：

pre $ 在范围内（5）：
＃vs，fs ，rs都是m * n个矩阵，得到了初始值，即vs [0]，fs [0]，rs [0]是已知的
#wnt使用这个foor循环来更新它们
vs [ 1 + 1] = vs [1] + fs [1]
fs [l + 1] =（rs [1] -re [1]）$ ​​b $ b rs [l + 1] = rs [ l] + vs [l]
＃然后这段代码给vs，fs，rs


如果我运行这种代码，那么只有当l = 5时，我才能得到答案...我怎么能让他们开始循环？即l = 0获得vs [1]，fs [1]，rs [1 ]，那么l = 1就得到了vs [2]，rs [2]，fs [2] ......等等的值，但python给出了不同的fs数组，对应于不同的值我怎样才能使他们成为一块？只是更新行，谢谢

解决方案

所有的编程语言都是一种运行一段代码的机制。

这段代码：

 对于范围（5）中的我：
 print i 
  

可以这样认为：
$ b $ pre $ i = 0
print i
i = 1
print i
i = 2
print i
i = 3
print i
i = 4
打印i


所以你看，发生了什么不是 i 同时获得值0,1,2,3,4 ，而是按顺序。

I假设当你说call a，它只给5时，你的意思是这样的：

  ）：
a = i + 1 
打印一个
  

em> last 值。每次循环迭代时，语句 a = i + 1 都会覆盖最后一个值 a 。
$ b

代码基本上按顺序运行，从上到下，for循环是使代码返回并重新运行的一种方式，对于其中一个变量。

我希望这能回答你的问题。

all,I am not really understand for loop in the following,can anyone give some tips?thanks in advance

for i in range(5):
      print i

then it gives 0,1,2,3,4 is that python assign 0,1,2,3,4 to i at the same time? however if i wrote:

for i in range(5):
      a=i+1

then I call a, it gives 5 only, but if i add ''print a'' it gives 1,2,3,4,5 .So my question is what is the difference here? i is a string or a list or something else? or maybe can anyone help me to sort out:

for l in range(5):
    #vs,fs,rs are all m*n matrixs,got initial values in,i.e vs[0],fs[0],rs[0] are known
    #want use this foor loop to update them
    vs[l+1]=vs[l]+fs[l]
    fs[l+1]=((rs[l]-re[l])
    rs[l+1]=rs[l]+vs[l]
#then this code gives vs,fs,rs

if i run this kind of code, then I will get the answer only when l=5...how can I make them start looping?i.e l=0 got values for vs[1],fs[1],rs[1], then l=1 got values for vs[2],rs[2],fs[2]......and so on.but python gives different arrays of fs,vs,rs, correspond to different value of l, how can I make them one piece? just update rows,thanks

解决方案

A "for loop" in most, if not all, programming languages is a mechanism to run a piece of code more than once.

This code:

for i in range(5):
    print i

can be thought of working like this:

i = 0
print i
i = 1
print i
i = 2
print i
i = 3
print i
i = 4
print i

So you see, what happens is not that i gets the value 0, 1, 2, 3, 4 at the same time, but rather sequentially.

I assume that when you say "call a, it gives only 5", you mean like this:

for i in range(5):
    a=i+1
print a

this will print the last value that a was given. Every time the loop iterates, the statement a=i+1 will overwrite the last value a had with the new value.

Code basically runs sequentially, from top to bottom, and a for loop is a way to make the code go back and something again, with a different value for one of the variables.

I hope this answered your question.

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