The .read_csv function does what you want:
pd.read_csv('c:/~/trainSetRel3.txt', sep='\t')
If you have a header, you can pass header=0.
pd.read_csv('c:/~/trainSetRel3.txt', sep='\t', header=0)
Note: Prior 17.0, pd.DataFrame.from_csv was used (it is now deprecated and the .from_csv documentation link redirects to the page for pd.read_csv).