need to get read names that have alt ref from a bamfile

so far i was able to write this but i am not sure what syntax to use after my for loop to query:

ref= 'T'
alt = 'C'
samfile= pysam.Samfile('bamfile', 'rb')
for pileupcolumn in samfile.pileup("2", start -1 , end):
    for pileupread in pileupcolumn.pileups:
        pileupread.alt_base?

Could some one help me with syntax thanks