The available columns for any given table are fetched from a system table called "sys_tablecolumns". A specific table name is provided in the WHERE criteria to restrict the table from which the column information is fetched:

import cdata.bigcommerce as mod
conn = mod.connect("AuthScheme=OAuth;InitiateOAuth=GETANDREFRESH;OAuthClientId=YourClientId;OAuthClientSecret=YourClientSecret;StoreId='YoUrSToREId';CallbackURL='http://localhost:33333'")
cur = conn.cursor()
cmd = "SELECT * FROM sys_tablecolumns WHERE TableName = 'Customers'"
cur.execute(cmd)
rs = cur.fetchall()
for row in rs:
	print(row)