import re
text = "col1 = 'Test String' , col2= 'Next Test String',col3='Last Text String', col4=37"
pattern = r"([^,\s=]+)\s*=\s*(?:'([^']*)'|(\S+))"
matches = re.findall(pattern, text)
print( dict([(x, z or y) for x,y,z in matches]) )
aW1wb3J0IHJlCnRleHQgPSAiY29sMSA9ICdUZXN0IFN0cmluZycgLCBjb2wyPSAnTmV4dCBUZXN0IFN0cmluZycsY29sMz0nTGFzdCBUZXh0IFN0cmluZycsIGNvbDQ9MzciCnBhdHRlcm4gPSByIihbXixccz1dKylccyo9XHMqKD86JyhbXiddKiknfChcUyspKSIKbWF0Y2hlcyA9IHJlLmZpbmRhbGwocGF0dGVybiwgdGV4dCkKcHJpbnQoIGRpY3QoWyh4LCB6IG9yIHkpIGZvciB4LHkseiBpbiBtYXRjaGVzXSkgKQ==