从 Python 中的 stdin 读取整数
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Reading in integer from stdin in Python
提问by Phil Kurtis
I have the following piece of code where I take in an integer n from stdin, convert it to binary, reverse the binary string, then convert back to integer and output it.
我有以下一段代码，我从 stdin 接收一个整数 n，将其转换为二进制，反转二进制字符串，然后转换回整数并输出它。
import sys
def reversebinary():
n = str(raw_input())
bin_n = bin(n)[2:]
revbin = "".join(list(reversed(bin_n)))
return int(str(revbin),2)
reversebinary()
However, I'm getting this error:
但是，我收到此错误：
Traceback (most recent call last):
File "reversebinary.py", line 18, in <module>
reversebinary()
File "reversebinary.py", line 14, in reversebinary
bin_n = bin(n)[2:]
TypeError: 'str' object cannot be interpreted as an index
I'm unsure what the problem is.
我不确定问题是什么。
采纳答案by Martijn Pieters
You are passing a string to the bin()function:
您正在向bin()函数传递一个字符串：
>>> bin('10')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: 'str' object cannot be interpreted as an index
Give it a integer instead:
给它一个整数：
>>> bin(10)
'0b1010'
by turning the raw_input()result to int():
通过将raw_input()结果变为int()：
n = int(raw_input())
Tip: you can easily reverse a string by giving it a negative slice stride:
提示：您可以通过给它一个负切片步幅来轻松反转字符串：
>>> 'forward'[::-1]
'drawrof'
so you can simplify your function to:
因此您可以将您的功能简化为：
def reversebinary():
n = int(raw_input())
bin_n = bin(n)[2:]
revbin = bin_n[::-1]
return int(revbin, 2)
or even:
甚至：
def reversebinary():
n = int(raw_input())
return int(bin(n)[:1:-1], 2)
回答by James Holderness
You want to convert the input to an integer not a string - it's already a string. So this line:
您想将输入转换为整数而不是字符串 - 它已经是字符串。所以这一行：
n = str(raw_input())
should be something like this:
应该是这样的：
n = int(raw_input())
回答by Mike Müller
It is raw input, i.e. a string but you need an int:
它是原始输入，即一个字符串，但您需要一个 int：
bin_n = bin(int(n))
回答by Tomá? Divi?
bintakes integer as parameter and you are putting string there, you must convert to integer:
bin将整数作为参数并且您将字符串放在那里，您必须转换为整数：
import sys
def reversebinary():
n = int(raw_input())
bin_n = bin(n)[2:]
revbin = "".join(list(reversed(bin_n)))
return int(str(revbin),2)
reversebinary()
