Pandas: modify values in a column

Date: April 1st 2016
Last updated: April 1st 2016

Prepare data (use pd.read_sql)

import MySQLdb
import pandas as pd
db = MySQLdb.connect(host='localhost',user='duck',passwd='password',db='surfdiary')
df_mysql = pd.read_sql("""SELECT boardperformance, 
                                  boardlength, 
                                  boardwidth, 
                                  boardthickness, 
                                  boardvolume FROM surferprofile_board;""", 
                                  con = db)

Head of dataframe

#   boardperformance boardlength boardwidth boardthickness  boardvolume
#0                HP        5 10     18 3/8         2 3/16        24.69
#1                HP         6 0     18 5/8         2 5/16        27.17
#2                HP         6 2     18 3/4          2 3/8        28.25
#...

Access column data

df_mysql['boardvolume']

Modify values in a column
See convert string fraction to decimal for more info on the two functions used below (e.g. convert_feet_to_float).

from fractions import Fraction

df_mysql['boardlength'] = df_mysql['boardlength'].apply(convert_feet_to_float)
df_mysql['boardwidth'] = df_mysql['boardwidth'].apply(convert_my_string_to_float)
df_mysql['boardthickness'] = df_mysql['boardthickness'].apply(convert_my_string_to_float)

Head of dataframe

#   boardperformance  boardlength  boardwidth  boardthickness  boardvolume
#0                HP     5.833333     18.3750        2.187500        24.69
#1                HP     6.000000     18.6250        2.312500        27.17
#2                HP     6.166667     18.7500        2.375000        28.25
#...