pandas DataFrame的 applymap() 函数可以对DataFrame里的每个值进行处理,然后返回一个新的DataFrame:
import pandas as pd df = pd.DataFrame({ ‘a‘: [1, 2, 3], ‘b‘: [10, 20, 30], ‘c‘: [5, 10, 15] }) def add_one(x): return x + 1 print df.applymap(add_one)
a b c
0 2 11 6
1 3 21 11
2 4 31 16
一个栗子:
这里有一组数据是10个学生的两次考试成绩,要求把成绩转换成ABCD等级:
转换规则是:
90-100 -> A
80-89 -> B
70-79 -> C
60-69 -> D
0-59 -> F
grades_df = pd.DataFrame( data={‘exam1‘: [43, 81, 78, 75, 89, 70, 91, 65, 98, 87], ‘exam2‘: [24, 63, 56, 56, 67, 51, 79, 46, 72, 60]}, index=[‘Andre‘, ‘Barry‘, ‘Chris‘, ‘Dan‘, ‘Emilio‘, ‘Fred‘, ‘Greta‘, ‘Humbert‘, ‘Ivan‘, ‘James‘] )
def convert_to_letter(score): if (score >= 90): return ‘A‘ elif (score >= 80): return ‘B‘ elif (score >= 70): return ‘C‘ elif (score >= 60): return ‘D‘ else: return ‘F‘ def convert_grades(grades): return grades.applymap(convert_to_letter)
print convert_grades(grades_df)
exam1 exam2
Andre F F
Barry B D
Chris C F
Dan C F
Emilio B D
Fred C F
Greta A C
Humbert D F
Ivan A C
James B D