我有一个列是unix时间戳。我想将此列转换为%y-%m-%d格式的日期。只是为了测试我在下面执行的to_datetime()函数，它按预期工作，并以类似2015-05-12 00:11:30的格式给我列：
df['time'] = pd.to_datetime(df['time'], unit='s')
当我添加format参数时如下所示，我收到错误：
df['time'] = pd.to_datetime(df['time'], unit='s', format='%d/%m/%Y')
错误为ValueError: time data 1431389490 does not match format '%d/%m/%Y'
如何剥离小时，分钟和秒钟，以便我只留下2014-05-12？
答案 0 :(得分：4)
如果您只想提取日期，可以在转换为datetime后的第二步中执行此操作：
datetime.date这将丢弃有关小时和分钟的信息，但您可以轻松使用生成的列/系列，因为结果是#include<Windows.h>
//==============================================================================
namespace wreg {
//------------------------------------------------------------------------------
using t_oshandle = HKEY;
struct t_api
{
static constexpr
auto open_key = ::RegOpenKeyExA;
// Tried all of these :
// RegOpenKeyExA; &RegOpenKeyExA; (::RegOpenKeyExA); (RegOpenKeyExA); (&RegOpenKeyExA);
//
static
constexpr auto close_key = ::RegCloseKey;
};
//------------------------------------------------------------------------------
} // namespace wreg
//==============================================================================
template < typename T >
struct type_deduced; // see Scott Meyers' "Effective Modern C++"
#define TYPE_DEDUCED( nr , t ) type_deduced< t > dummy_ ## nr
int main ()
{
//type_deduced< decltype(RegOpenKeyExA) > s1;
//TYPE_DEDUCED( 1 , decltype(RegOpenKeyExA) ); // 'dummy_1' uses undefined struct 'type_deduced<LSTATUS (HKEY,LPCSTR,DWORD,REGSAM,PHKEY)>'
//TYPE_DEDUCED( 1a , decltype(::RegOpenKeyExA) ); // 'dummy_1a' uses undefined struct 'type_deduced<LSTATUS (HKEY,LPCSTR,DWORD,REGSAM,PHKEY)>'
//TYPE_DEDUCED( 3 , decltype(wreg::t_api::open_key) ); // 'dummy_3' uses undefined struct 'type_deduced<LSTATUS (__stdcall *const )(HKEY,LPCSTR,DWORD,REGSAM,PHKEY)>'
auto hk = wreg::t_oshandle{};
#define ORIGINAL_APPROACH 0
#ifdef ORIGINAL_APPROACH // faulty version
auto res = wreg::t_api::open_key( HKEY_LOCAL_MACHINE ,"SOFTWARE" ,0 ,KEY_READ ,&hk );
if (res == ERROR_SUCCESS)
{
res = wreg::t_api::close_key( hk );
}
#else // working version
auto open_key = ::RegOpenKeyExA;
auto res = open_key( HKEY_LOCAL_MACHINE ,"SOFTWARE" ,0 ,KEY_READ ,&hk );
if (res == ERROR_SUCCESS)
{
auto close_key = ::RegCloseKey;
res = close_key( hk );
}
#endif
return 0;
}
//==============================================================================
对象，例如减去以查找列与特定日期之间的天数。
如果您想保留有关小时和分钟的信息，但只是显示，则我不确定是否可能。