Satoshi's signature is encoded in a system called DER which is a subset of ASN.1.
There are two 32-byte numbers we need to extract. They are referred to as R and S respectively and are each prefixed by the bytes 0220 in the DER sequence. Instead of fully decoding the DER blob, just look for the prefixes and paste the R and S values.
# Satoshi's signature, from the input scriptSig of the tx to Hal Finney (block 170)
sig_der = """304402204e45e16932b8af514961a1d3a1a25fdf3f4f7732e9d624c6c61548ab5fb8cd410220181522ec8eca07de4860a4acdd12909d831cc56cbbac4622082221a8768d1d09"""