Pandas na_values: Treating custom strings as missing data

A file you’re loading into Python Pandas uses weird strings for missing values? Use the na_values parameter in read_* methods:

pd.read_csv(f, na_values='.') 
pd.read_csv(f, na_values=['.', '*']) # multiple 
pd.read_csv(f, na_values={'a':'.', 'b':'*'}) # per column