小编Paz*_*r80的帖子

好吧,所以我使用了很多输入命令,我明白在Python2中我可以这样做:

text = raw_input ('Text here')

但是现在我使用Python 3,我想知道它们之间有什么区别:

text = input('Text here')

和:

text = eval(input('Text here'))

我何时必须使用其中一个？

我开始学习C++,并尝试运行经典的Hello World程序:

#include <iostream>

using namespace std;

int main ()
{
  cout << "Hello, World!";
  return 0;
}

但是当我使用GCC在终端中编译它时,我总是得到错误:

Undefined symbols for architecture x86_64:
  "std::basic_string<char, std::char_traits<char>, std::allocator<char> >::size() const", referenced from:
      std::__verify_grouping(char const*, unsigned long, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)in ccpe3DPY.o
  "std::basic_string<char, std::char_traits<char>, std::allocator<char> >::operator[](unsigned long) const", referenced from:
      std::__verify_grouping(char const*, unsigned long, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)in ccpe3DPY.o
  "std::cout", referenced from:
      _main in ccpe3DPY.o
  "std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)", referenced from:
      _main in ccpe3DPY.o …

我已经看过很多次但是从来没有理解asPython 3.x中的命令.你能用简单的英语解释一下吗？

当我编写每个C++程序时,例如:

#include <iostream>
#include <string>

using namespace std;

int main()
{
    int n;
    cout << "Tell me where to start: ";
    cin >> n;
    while (n>0) {
        cout << n << "\n";
        n = n-1;
    }
    cout << "FIRE!";
    return 0;
}

我用G ++编译它,当我运行它时,它运行良好,但是当它完成时它会在程序的最后一个单词之后显示"logout"字样,如下所示:

Tell me where to start: 10
10
9
8
7
6
5
4
3
2
1
FIRE!logout

[Process completed]

为什么？我该如何删除它？