python /C : Parse all values at once for return to Python?

Question

如果您要将大量值从 C 输出到 Python 中的字典，是否有比以下更好(更快且更不容易出错)的方法:

    return Py_BuildValue("{s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:d,s:(i,i,i,i),s:(i,i,i,i),s:(i,i,i,i)}",
            "jd\0",             spa.jd, //Julian day
            "jc\0",             spa.jc, //Julian century
            "jde\0",            spa.jde, //Julian ephemeris day
            "jce\0",            spa.jce, //Julian ephemeris century
            "jme\0",            spa.jme, //Julian ephemeris millennium
            "l\0",              spa.l, //earth heliocentric longitude [degrees]
            "b\0",              spa.b, //earth heliocentric latitude [degrees]
            "r\0",              spa.r,     //earth radius vector [Astronomical Units, AU]
            "theta\0",          spa.theta, //geocentric longitude [degrees]
            "beta\0",           spa.beta, //geocentric latitude [degrees]
            "x0\0",             spa.x0, //mean elongation (moon-sun) [degrees]
            "x1\0",             spa.x1, //mean anomaly (sun) [degrees]
            "x2\0",             spa.x2, //mean anomaly (moon) [degrees]
            "x3\0",             spa.x3, //argument latitude (moon) [degrees]
            "x4\0",             spa.x4, //ascending longitude (moon) [degrees]
            "del_psi\0",        spa.del_psi, //nutation longitude [degrees]
            "del_epsilon\0",    spa.del_epsilon, //nutation obliquity [degrees]
            "epsilon0\0",       spa.epsilon0, //ecliptic mean obliquity [arc seconds]
            "epsilon\0",        spa.epsilon, //ecliptic true obliquity  [degrees]
            "del_tau\0",        spa.del_tau, //aberration correction [degrees]
            "lamda\0",          spa.lamda, //apparent sun longitude [degrees]
            "nu0\0",            spa.nu0, //Greenwich mean sidereal time [degrees]
            "nu\0",             spa.nu, //Greenwich sidereal time [degrees]
            "alpha\0",          spa.alpha, //geocentric sun right ascension [degrees]
            "delta\0",          spa.delta, //geocentric sun declination [degrees]
            "h\0",              spa.h, //observer hour angle [degrees]
            "xi\0",             spa.xi, //sun equatorial horizontal parallax [degrees]
            "del_alpha\0",      spa.del_alpha, //sun right ascension parallax [degrees]
            "delta_prime\0",    spa.delta_prime, //topocentric sun declination [degrees]
            "alpha_prime\0",    spa.alpha_prime, //topocentric sun right ascension [degrees]
            "h_prime\0",        spa.h_prime, //topocentric local hour angle [degrees],
            "h0_prime\0",       spa.h0_prime,
            "delta_zero\0",     spa.delta_zero,
            "e0\0",             spa.e0, //topocentric elevation angle (uncorrected) [degrees]
            "del_e\0",          spa.del_e, //atmospheric refraction correction [degrees]
            "e\0",              spa.e, //topocentric elevation angle (corrected) [degrees]
            "eot\0",            spa.eot, //equation of time [minutes]
            "srha\0",           spa.srha, //sunrise hour angle [degrees]
            "ssha\0",           spa.ssha, //sunset hour angle [degrees]
            "sta\0",            spa.sta, //sun transit altitude [degrees]
            "zenith\0",         spa.zenith, //topocentric zenith angle [degrees]
            "azimuth180\0",     spa.azimuth180, //topocentric azimuth angle (westward from south) [-180 to 180 degrees]
            "azimuth\0",        spa.azimuth, //topocentric azimuth angle (eastward from north) [   0 to 360 degrees]
            "incidence\0",      spa.incidence, //surface incidence angle [degrees]
            "_suntransit\0",    spa.suntransit, //local sun transit time (or solar noon) [fractional hour]
            "_sunrise\0",       spa.sunrise, //local sunrise time (+/- 30 seconds) [fractional hour]
            "_sunset\0",        spa.sunset, //local sunset time (+/- 30 seconds) [fractional hour]
            "sunrise\0",        sunrise_hour, sunrise_min, sunrise_sec, sunrise_microsec,
            "sunset\0",         sunset_hour, sunset_min, sunset_sec, sunset_microsec,
            "noon\0",           transit_hour, transit_min, transit_sec, transit_microsec
            );

Answer 1

我同意@Martin v. Löwis 关于使用 C 预处理器及其宏功能至少减轻一些设置和维护您正在做的事情的负担。如果您正确定义了这些宏，您可以安排将所有定义信息放在单个头文件中的一个位置，避免重复自己。

基本上，您需要关于每个项目或键值对的两条信息，这些信息将进入您正在构建的字典中。一个是放在 Py_BuildValue() 的格式字符串参数中的内容，第二个是键的来源和它的关联值。

您可以通过定义然后重新定义任务所需的宏来提取这两组信息中的每一个。对于您的示例，可以创建以下头文件。请注意，根据 #included 时定义的是 FORMAT 还是 FIELDS，如何定义两组不同的宏中的一组。

// builddict.h -- for defining Py_BuildValue() arguments

// define apppropriate macros for current usage
#ifdef FORMAT
    #define SPA_FIELD_LAST(FIELD)           "s:d"
    #define SPA_FIELD(FIELD)                SPA_FIELD_LAST(FIELD)", "
    #define TIME_FIELD_LAST(NAME)           "s:(i,i,i,i)"
    #define TIME_FIELD(NAME)                TIME_FIELD_LAST(NAME)", "
    #define TIME_KEY_FIELD_LAST(KEY,NAME)   "s:(i,i,i,i)"
    #define TIME_KEY_FIELD(KEY,NAME)        TIME_KEY_FIELD_LAST(KEY,NAME)", "
    #undef FORMAT
#elif defined FIELDS
    #define SPA_FIELD_LAST(FIELD)           #FIELD, spa.FIELD
    #define SPA_FIELD(FIELD)                SPA_FIELD_LAST(FIELD),
    #define TIME_FIELD_LAST(NAME)           #NAME, NAME##_hour, NAME##_min, NAME##_sec, NAME##_microsec
    #define TIME_FIELD(NAME)                TIME_FIELD_LAST(NAME),
    #define TIME_KEY_FIELD_LAST(KEY,NAME)   #KEY, NAME##_hour, NAME##_min, NAME##_sec, NAME##_microsec
    #define TIME_KEY_FIELD(KEY,NAME)        TIME_KEY_FIELD_LAST(KEY,NAME),
    #undef FIELDS
#else
    #error neither FORMAT nor FIELDS usage macros are defined
#endif

SPA_FIELD(jd)               // Julian day
SPA_FIELD(jc)               // Julian century
SPA_FIELD(jde)              // Julian ephemeris day
SPA_FIELD(jce)              // Julian ephemeris century
SPA_FIELD(jme)              // Julian ephemeris millennium
SPA_FIELD(l)                // earth heliocentric longitude [degrees]
SPA_FIELD(b)                // earth heliocentric latitude [degrees]
SPA_FIELD(r)                // earth radius vector [Astronomical Units)  AU]
SPA_FIELD(theta)            // geocentric longitude [degrees]
SPA_FIELD(beta)             // geocentric latitude [degrees]
SPA_FIELD(x0)               // mean elongation (moon-sun) [degrees]
SPA_FIELD(x1)               // mean anomaly (sun) [degrees]
SPA_FIELD(x2)               // mean anomaly (moon) [degrees]
SPA_FIELD(x3)               // argument latitude (moon) [degrees]
SPA_FIELD(x4)               // ascending longitude (moon) [degrees]
SPA_FIELD(del_psi)          // nutation longitude [degrees]
SPA_FIELD(del_epsilon)      // nutation obliquity [degrees]
SPA_FIELD(epsilon0)         // ecliptic mean obliquity [arc seconds]
SPA_FIELD(epsilon)          // ecliptic true obliquity  [degrees]
SPA_FIELD(del_tau)          // aberration correction [degrees]
SPA_FIELD(lamda)            // apparent sun longitude [degrees]
SPA_FIELD(nu0)              // Greenwich mean sidereal time [degrees]
SPA_FIELD(nu)               // Greenwich sidereal time [degrees]
SPA_FIELD(alpha)            // geocentric sun right ascension [degrees]
SPA_FIELD(delta)            // geocentric sun declination [degrees]
SPA_FIELD(h)                // observer hour angle [degrees]
SPA_FIELD(xi)               // sun equatorial horizontal parallax [degrees]
SPA_FIELD(del_alpha)        // sun right ascension parallax [degrees]
SPA_FIELD(delta_prime)      // topocentric sun declination [degrees]
SPA_FIELD(alpha_prime)      // topocentric sun right ascension [degrees]
SPA_FIELD(h_prime)          // topocentric local hour angle [degrees])
SPA_FIELD(h0_prime)
SPA_FIELD(delta_zero)
SPA_FIELD(e0)               // topocentric elevation angle (uncorrected) [degrees]
SPA_FIELD(del_e)            // atmospheric refraction correction [degrees]
SPA_FIELD(e)                // topocentric elevation angle (corrected) [degrees]
SPA_FIELD(eot)              // equation of time [minutes]
SPA_FIELD(srha)             // sunrise hour angle [degrees]
SPA_FIELD(ssha)             // sunset hour angle [degrees]
SPA_FIELD(sta)              // sun transit altitude [degrees]
SPA_FIELD(zenith)           // topocentric zenith angle [degrees]
SPA_FIELD(azimuth180)       // topocentric azimuth angle (westward from south) [-180 to 180 degrees]
SPA_FIELD(azimuth)          // topocentric azimuth angle (eastward from north) [   0 to 360 degrees]
SPA_FIELD(incidence)        // surface incidence angle [degrees]
SPA_FIELD(suntransit)       // local sun transit time (or solar noon) [fractional hour]
SPA_FIELD(sunrise)          // local sunrise time (+/- 30 seconds) [fractional hour]
SPA_FIELD(sunset)           // local sunset time (+/- 30 seconds) [fractional hour]
TIME_FIELD(sunrise)
TIME_FIELD(sunset)
TIME_KEY_FIELD_LAST(noon, transit)  // must use a xxx_LAST macro on last one

// clean up to prevent warnings about redefining macros
#undef SPA_FIELD_LAST
#undef SPA_FIELD
#undef TIME_FIELD_LAST
#undef TIME_FIELD
#undef TIME_KEY_FIELD_LAST
#undef TIME_KEY_FIELD

一旦您完成所有设置，您的 build_dict() 函数将变得相当简短并且独立于字典的实际内容:

// build format string using header
char format_string[] = "{"
    #define FORMAT
    #include "builddict.h"
"}";

// use header again to build list of fields
PyObject* build_dict(SPA spa)
{
    return Py_BuildValue(format_string,
        #define FIELDS
        #include "builddict.h"
    );
}

虽然这不能完全自动化该过程，但可以提供很大帮助。可能有其他可用的文本处理或 C 接口(interface)工具(或者您可以编写自己的工具)来进一步帮助您创建这个单一的头文件，因为它采用非常统一的格式。