Yes, it's a good idea. But unfortunatelly it's far from trivial to securely wipe data from memory. Modern compilers, operating system and CPUs make it really, really hard.
For instance you never know where your computer has stored sensitive data. CPUs have L1, L2 and shared L3 caches. NUMA (even ccNUMA) can do fancy stuff with your data until you enforce a memory barrier. The operating system may decide to swap the memory pages to disk, too. mlock() could help but it requires extra capabilities and is hard to use, because it operates on pages.
A simple call to memset() is wrong most of the time as well. Every state-of-the-art compiler will silently remove memset()-based cleanup code. C11 has introduced memset_s() but it's not yet available in most CRTs. See
You can try code like
static void * (* const volatile __memset_vp)(void *, int, size_t) = (memset);
(*__memset_vp)(s, c, n);
memset(s, c, n);
asm volatile("" : : "r"(s) : "memory"); /* may need GCC */
SecureZeroMemory(s, n); /* Windows only */
For CPython you have to implement your own data type in C and wipe memory in its deallocation function. Python's core types won't get a flag for secure wiping anytime soon (most like never).