diff -Naur Python-3.7.0-orig/Include/internal/pystate.h Python-3.7.0/Include/internal/pystate.h
--- Python-3.7.0-orig/Include/internal/pystate.h	2018-06-27 06:07:35.000000000 +0300
+++ Python-3.7.0/Include/internal/pystate.h	2018-07-12 10:21:48.703201600 +0300
@@ -43,7 +43,8 @@
     wchar_t *prefix;
 #ifdef MS_WINDOWS
     wchar_t *dll_path;
-#else
+#endif
+#ifndef _MSC_VER
     wchar_t *exec_prefix;
 #endif
     /* Set by Py_SetPath(), or computed by _PyPathConfig_Init() */
diff -Naur Python-3.7.0-orig/Include/pylifecycle.h Python-3.7.0/Include/pylifecycle.h
--- Python-3.7.0-orig/Include/pylifecycle.h	2018-07-12 10:21:48.141600600 +0300
+++ Python-3.7.0/Include/pylifecycle.h	2018-07-12 10:21:48.718801700 +0300
@@ -131,7 +131,7 @@
     size_t value_size);
 #endif
 PyAPI_FUNC(void)      Py_SetPath(const wchar_t *);
-#ifdef MS_WINDOWS
+#ifdef _MSC_VER
 int _Py_CheckPython3(void);
 #endif
 
diff -Naur Python-3.7.0-orig/Modules/getpath.c Python-3.7.0/Modules/getpath.c
--- Python-3.7.0-orig/Modules/getpath.c	2018-07-12 10:21:48.157200700 +0300
+++ Python-3.7.0/Modules/getpath.c	2018-07-12 10:21:48.734401700 +0300
@@ -11,6 +11,11 @@
 #  include <mach-o/dyld.h>
 #endif
 
+#ifdef MS_WINDOWS
+#include <windows.h>
+#include <shlwapi.h>
+#endif
+
 /* Search in some common locations for the associated Python libraries.
  *
  * Two directories must be found, the platform independent directory
@@ -131,8 +136,33 @@
 } PyCalculatePath;
 
 static const wchar_t delimiter[2] = {DELIM, '\0'};
-static const wchar_t separator[2] = {SEP, '\0'};
+static wchar_t separator[2] = {SEP, '\0'};
 
+static int
+is_sep(wchar_t ch)
+{
+#ifdef _WIN32
+    return ch == SEP || ch == ALTSEP;
+#else
+    return ch == SEP;
+#endif
+}
+
+static int
+is_absolute(wchar_t *path)
+{
+#ifdef _WIN32
+    size_t i = wcslen(path);
+    if (i >= 3) {
+        if (iswalpha(path[0]) && path[1] == L':' && is_sep(path[2])) {
+            return 1;
+        }
+    }
+    return 0;
+#else
+    return path[0] == SEP;
+#endif
+}
 
 /* Get file status. Encode the path to the locale encoding. */
 static int
@@ -155,7 +185,7 @@
 reduce(wchar_t *dir)
 {
     size_t i = wcslen(dir);
-    while (i > 0 && dir[i] != SEP)
+    while (i > 0 && !is_sep(dir[i]))
         --i;
     dir[i] = '\0';
 }
@@ -239,13 +269,13 @@
 joinpath(wchar_t *buffer, wchar_t *stuff)
 {
     size_t n, k;
-    if (stuff[0] == SEP) {
+    if (is_sep(stuff[0])) {
         n = 0;
     }
     else {
         n = wcslen(buffer);
-        if (n > 0 && buffer[n-1] != SEP && n < MAXPATHLEN) {
-            buffer[n++] = SEP;
+        if (n > 0 && !is_sep(buffer[n-1]) && n < MAXPATHLEN) {
+            buffer[n++] = Py_GetSepW(buffer);
         }
     }
     if (n > MAXPATHLEN) {
@@ -265,7 +295,7 @@
 static void
 copy_absolute(wchar_t *path, wchar_t *p, size_t pathlen)
 {
-    if (p[0] == SEP) {
+    if (is_absolute(p)) {
         wcscpy(path, p);
     }
     else {
@@ -274,7 +304,7 @@
             wcscpy(path, p);
             return;
         }
-        if (p[0] == '.' && p[1] == SEP) {
+        if (p[0] == '.' && is_sep(p[1])) {
             p += 2;
         }
         joinpath(path, p);
@@ -288,7 +318,7 @@
 {
     wchar_t buffer[MAXPATHLEN+1];
 
-    if (path[0] == SEP) {
+    if (is_absolute(path)) {
         return;
     }
     copy_absolute(buffer, path, MAXPATHLEN+1);
@@ -323,6 +353,7 @@
     wcsncpy(prefix, calculate->argv0_path, MAXPATHLEN);
     prefix[MAXPATHLEN] = L'\0';
     joinpath(prefix, L"Modules/Setup");
+    Py_NormalizeSepsW(prefix);
     if (isfile(prefix)) {
         /* Check VPATH to see if argv0_path is in the build directory. */
         vpath = Py_DecodeLocale(VPATH, NULL);
@@ -333,6 +364,7 @@
             PyMem_RawFree(vpath);
             joinpath(prefix, L"Lib");
             joinpath(prefix, LANDMARK);
+            Py_NormalizeSepsW(prefix);
             if (ismodule(prefix)) {
                 return -1;
             }
@@ -394,12 +426,21 @@
      * return the compiled-in defaults instead.
      */
     if (calculate->prefix_found > 0) {
+#ifdef _WIN32
+        wchar_t drive_root[3];
+        memset(drive_root, 0, sizeof(drive_root));
+        wcsncpy(drive_root, prefix, 3);
+#endif
         reduce(prefix);
         reduce(prefix);
         /* The prefix is the root directory, but reduce() chopped
          * off the "/". */
         if (!prefix[0]) {
+#ifdef _WIN32
+            wcsncpy(prefix, drive_root, 3);
+#else
             wcscpy(prefix, separator);
+#endif
         }
     }
     else {
@@ -454,6 +495,7 @@
                 wcsncpy(exec_prefix, calculate->argv0_path, MAXPATHLEN);
                 exec_prefix[MAXPATHLEN] = L'\0';
                 joinpath(exec_prefix, rel_builddir_path);
+                Py_NormalizeSepsW(exec_prefix);
                 PyMem_RawFree(rel_builddir_path );
                 return -1;
             }
@@ -501,6 +543,7 @@
         }
         wcsncpy(exec_prefix, calculate->exec_prefix, MAXPATHLEN);
         joinpath(exec_prefix, L"lib/lib-dynload");
+        Py_NormalizeSepsW(exec_prefix);
     }
     /* If we found EXEC_PREFIX do *not* reduce it!  (Yet.) */
 }
@@ -510,11 +553,20 @@
 calculate_reduce_exec_prefix(PyCalculatePath *calculate, wchar_t *exec_prefix)
 {
     if (calculate->exec_prefix_found > 0) {
+#ifdef _WIN32
+        wchar_t drive_root[3];
+        memset(drive_root, 0, sizeof(drive_root));
+        wcsncpy(drive_root, exec_prefix, 3);
+#endif
         reduce(exec_prefix);
         reduce(exec_prefix);
         reduce(exec_prefix);
         if (!exec_prefix[0]) {
+#ifdef _WIN32
+            wcsncpy(exec_prefix, drive_root, 3);
+#else
             wcscpy(exec_prefix, separator);
+#endif
         }
     }
     else {
@@ -523,6 +575,52 @@
 }
 
 
+#ifdef MS_WINDOWS
+static int
+GetWindowsModulePaths(wchar_t *progpath)
+{
+    int result = 0;
+    wchar_t program_full_path[MAXPATHLEN+1];
+    memset(program_full_path, 0, sizeof(program_full_path));
+
+    if (GetModuleFileNameW(NULL, program_full_path, MAXPATHLEN)) {
+        result = 1;
+        Py_NormalizeSepsW(program_full_path);
+    }
+
+    wcscpy(progpath, program_full_path);
+    return result;
+}
+
+
+static _PyInitError
+get_dll_path(_PyPathConfig *config)
+{
+    wchar_t dll_path[MAXPATHLEN+1];
+    memset(dll_path, 0, sizeof(dll_path));
+
+#ifdef Py_ENABLE_SHARED
+    extern HANDLE PyWin_DLLhModule;
+    if (PyWin_DLLhModule) {
+        if (GetModuleFileNameW(PyWin_DLLhModule, dll_path, MAXPATHLEN)) {
+            Py_NormalizeSepsW(dll_path);
+        } else {
+            dll_path[0] = 0;
+        }
+    }
+#else
+    dll_path[0] = 0;
+#endif
+
+    config->dll_path = _PyMem_RawWcsdup(dll_path);
+    if (config->dll_path == NULL) {
+        return _Py_INIT_NO_MEMORY();
+    }
+    return _Py_INIT_OK();
+}
+#endif /* MS_WINDOWS */
+
+
 static _PyInitError
 calculate_program_full_path(const _PyCoreConfig *core_config,
                             PyCalculatePath *calculate, _PyPathConfig *config)
@@ -544,7 +642,7 @@
      * other way to find a directory to start the search from.  If
      * $PATH isn't exported, you lose.
      */
-    if (wcschr(core_config->program_name, SEP)) {
+    if (wcschr(core_config->program_name, Py_GetSepW(core_config->program_name))) {
         wcsncpy(program_full_path, core_config->program_name, MAXPATHLEN);
     }
 #ifdef __APPLE__
@@ -570,6 +668,10 @@
         PyMem_RawFree(path);
     }
 #endif /* __APPLE__ */
+#ifdef MS_WINDOWS
+    else if(GetWindowsModulePaths(program_full_path)) {
+    }
+#endif /* MS_WINDOWS */
     else if (calculate->path_env) {
         wchar_t *path = calculate->path_env;
         while (1) {
@@ -602,7 +704,7 @@
     else {
         program_full_path[0] = '\0';
     }
-    if (program_full_path[0] != SEP && program_full_path[0] != '\0') {
+    if (!is_absolute(program_full_path)) {
         absolutize(program_full_path);
     }
 
@@ -743,6 +845,7 @@
         wcsncpy(calculate->zip_path, calculate->prefix, MAXPATHLEN);
     }
     joinpath(calculate->zip_path, L"lib/python00.zip");
+    Py_NormalizeSepsW(calculate->zip_path);
 
     /* Replace "00" with version */
     size_t bufsz = wcslen(calculate->zip_path);
@@ -768,7 +871,7 @@
     while (1) {
         wchar_t *delim = wcschr(defpath, DELIM);
 
-        if (defpath[0] != SEP) {
+        if (!is_absolute(defpath)) {
             /* Paths are relative to prefix */
             bufsz += prefixsz;
         }
@@ -785,6 +888,14 @@
 
     bufsz += wcslen(calculate->zip_path) + 1;
     bufsz += wcslen(exec_prefix) + 1;
+#ifdef MS_WINDOWS
+    if (is_absolute(prefix)) {
+        bufsz += wcslen(prefix) + 1;
+    }
+    if (is_absolute(calculate->argv0_path)) {
+        bufsz += wcslen(calculate->argv0_path) + 1;
+    }
+#endif
 
     /* Allocate the buffer */
     wchar_t *buf = PyMem_RawMalloc(bufsz * sizeof(wchar_t));
@@ -810,9 +921,9 @@
     while (1) {
         wchar_t *delim = wcschr(defpath, DELIM);
 
-        if (defpath[0] != SEP) {
+        if (!is_absolute(defpath)) {
             wcscat(buf, prefix);
-            if (prefixsz >= 2 && prefix[prefixsz - 2] != SEP &&
+            if (prefixsz >= 2 && !is_sep(prefix[prefixsz - 2]) &&
                 defpath[0] != (delim ? DELIM : L'\0'))
             {
                 /* not empty */
@@ -833,6 +944,16 @@
         defpath = delim + 1;
     }
     wcscat(buf, delimiter);
+#ifdef MS_WINDOWS
+    if (is_absolute(prefix)) {
+        wcscat(buf, prefix);
+        wcscat(buf, delimiter);
+    }
+    if (is_absolute(calculate->argv0_path)) {
+        wcscat(buf, calculate->argv0_path);
+        wcscat(buf, delimiter);
+    }
+#endif
 
     /* Finally, on goes the directory for dynamic-load modules */
     wcscat(buf, exec_prefix);
@@ -859,15 +980,19 @@
     if (!calculate->pythonpath) {
         return DECODE_LOCALE_ERR("PYTHONPATH define", len);
     }
+    Py_NormalizeSepsW(calculate->pythonpath);
     calculate->prefix = Py_DecodeLocale(PREFIX, &len);
     if (!calculate->prefix) {
         return DECODE_LOCALE_ERR("PREFIX define", len);
     }
+    Py_NormalizeSepsW(calculate->prefix);
     calculate->exec_prefix = Py_DecodeLocale(EXEC_PREFIX, &len);
     if (!calculate->prefix) {
         return DECODE_LOCALE_ERR("EXEC_PREFIX define", len);
     }
-    calculate->lib_python = Py_DecodeLocale("lib/python" VERSION, &len);
+    Py_NormalizeSepsW(calculate->exec_prefix);
+    const char *lib_python_VERSION = (Py_GetSepW(NULL) == L'/') ? "lib/python" VERSION : "lib\\python" VERSION;
+    calculate->lib_python = Py_DecodeLocale(lib_python_VERSION, &len);
     if (!calculate->lib_python) {
         return DECODE_LOCALE_ERR("EXEC_PREFIX define", len);
     }
@@ -892,6 +1017,13 @@
 {
     _PyInitError err;
 
+#ifdef MS_WINDOWS
+    err = get_dll_path(config);
+    if (_Py_INIT_FAILED(err)) {
+        return err;
+    }
+#endif
+
     err = calculate_program_full_path(core_config, calculate, config);
     if (_Py_INIT_FAILED(err)) {
         return err;
@@ -949,6 +1106,7 @@
 _PyPathConfig_Calculate(_PyPathConfig *config, const _PyCoreConfig *core_config)
 {
     PyCalculatePath calculate;
+    separator[0] = Py_GetSepW(NULL);
     memset(&calculate, 0, sizeof(calculate));
 
     _PyInitError err = calculate_init(&calculate, core_config);
diff -Naur Python-3.7.0-orig/Modules/posixmodule.c Python-3.7.0/Modules/posixmodule.c
--- Python-3.7.0-orig/Modules/posixmodule.c	2018-07-12 10:21:48.204000700 +0300
+++ Python-3.7.0/Modules/posixmodule.c	2018-07-12 10:21:48.765601700 +0300
@@ -3526,7 +3526,7 @@
         Py_END_ALLOW_THREADS
         /* FindNextFile sets error to ERROR_NO_MORE_FILES if
            it got to the end of the directory. */
-        if (!result && GetLastError() != ERROR_NO_MORE_FILES) {
+        if (!result && GetLastError() != 0 && GetLastError() != ERROR_NO_MORE_FILES) {
             Py_DECREF(list);
             list = path_error(path);
             goto exit;
diff -Naur Python-3.7.0-orig/Python/dynload_win.c Python-3.7.0/Python/dynload_win.c
--- Python-3.7.0-orig/Python/dynload_win.c	2018-07-12 10:21:08.969931800 +0300
+++ Python-3.7.0/Python/dynload_win.c	2018-07-12 10:21:48.781201800 +0300
@@ -202,7 +202,7 @@
     char funcname[258], *import_python;
     const wchar_t *wpathname;
 
-#ifndef _DEBUG
+#if !defined(_DEBUG) && defined(_MSC_VER)
     _Py_CheckPython3();
 #endif
 
diff -Naur Python-3.7.0-orig/Python/pathconfig.c Python-3.7.0/Python/pathconfig.c
--- Python-3.7.0-orig/Python/pathconfig.c	2018-07-12 10:21:48.235200800 +0300
+++ Python-3.7.0/Python/pathconfig.c	2018-07-12 10:21:48.796801800 +0300
@@ -140,7 +140,8 @@
     CLEAR(config->program_full_path);
 #ifdef MS_WINDOWS
     CLEAR(config->dll_path);
-#else
+#endif
+#ifndef _MSC_VER
     CLEAR(config->exec_prefix);
 #endif
     CLEAR(config->module_search_path);
@@ -253,7 +254,8 @@
     new_config.prefix = _PyMem_RawWcsdup(L"");
 #ifdef MS_WINDOWS
     new_config.dll_path = _PyMem_RawWcsdup(L"");
-#else
+#endif
+#ifndef _MSC_VER
     new_config.exec_prefix = _PyMem_RawWcsdup(L"");
 #endif
     new_config.module_search_path = _PyMem_RawWcsdup(path);
@@ -333,7 +335,7 @@
 wchar_t *
 Py_GetExecPrefix(void)
 {
-#ifdef MS_WINDOWS
+#ifdef _MSC_VER
     return Py_GetPrefix();
 #else
     pathconfig_global_init();