列处理——格式转换(考虑非法值)

----------------基于普通python

#first two elements of list legislators.
#[['Bassett', 'Richard', '1745-04-02', 'M', 'sen', 'DE', 'Anti-Administration', '1745'], ['Bland', 'Theodorick', '1742-03-21', 'M', 'rep', 'VA', '', '1742']]
#1745 is extract from 1745-04-02 as the birth year, but not all elements have valid birth years. Some birth year is ""

• 字符转换成数字格式

for row in legislators:
    try:
        row[7]=int(row[7])
    except Exception:
        row[7]=0

 

----------------基于numpy

matrix: world_alcohol

bad_value = ''
alcohol_consumption_float_column = None
#replace the bad value of the fifth column to 0
world_alcohol[:,4][world_alcohol[:,4] == bad_value] = '0'
#convert string to float
alcohol_consumption_float_column = world_alcohol[:,4].astype(float)
#but I don't know how to write the float value back to the matrix....