python学习四(处理数据)

head first python中的一个数据处理的例子

有四个U10选手的600米成绩，请取出每个选手跑的最快的3个时间。以下是四位选手的9次成绩

James

2-34,3:21,2.34,2.45,3.01,2:01,2:01,3:10,2-22

Julie

2.59,2.11,2:11,2:23,3-10,2-23,3:10,3.21,3-21

Mikey 

2:22,3.01,3:01,3.02,3:02,3.02,3:22,2.49,2:38

 Sarah

2:58,2.58,2:39,2-25,2-55,2:54,2.18,2:55,2:55

 代码如下：

def sanitize(time_string):
    if '-' in time_string:
        splitter = '-'
    elif ':' in time_string:
        splitter = ':'
    else:
        return(time_string)
    (mins, secs) = time_string.split(splitter)
    return(mins + '.' + secs)

def get_coach_data(filename): 
    try:
        with open(filename) as f:
            data = f.readline() 
        return(data.strip().split(','))
    except IOError as ioerr:
        print('File error: ' + str(ioerr))
        return(None)

james = get_coach_data('james.txt')
julie = get_coach_data('julie.txt')
mikey = get_coach_data('mikey.txt')
sarah = get_coach_data('sarah.txt')

print(sorted(set([sanitize(t) for t in james]))[0:3])
print(sorted(set([sanitize(t) for t in julie]))[0:3])
print(sorted(set([sanitize(t) for t in mikey]))[0:3])
print(sorted(set([sanitize(t) for t in sarah]))[0:3])

首先定义了一个模块sanitize清理数据，注意set集合中不允许重复记录，sorted会返回一个排序后的列表，不会修改原有的列表。

 打印结果

['2.01', '2.22', '2.34']
['2.11', '2.23', '2.59']
['2.22', '2.38', '2.49']
['2.18', '2.25', '2.39']

 例2：

提供另外一组成绩数据，数据中包括了运动员姓名，出生日期，及成绩。

打印出每个运动员姓名，及最快的三次成绩 

def sanitize(time_string):
    if '-' in time_string:
        splitter = '-'
    elif ':' in time_string:
        splitter = ':'
    else:
        return(time_string)
    (mins, secs) = time_string.split(splitter)
    return(mins + '.' + secs)

def get_coach_data(filename):
    try:
        with open(filename) as f:
            data = f.readline()
        templ = data.strip().split(',')
        return({'Name' : templ.pop(0),
                'DOB'  : templ.pop(0),
                'Times': str(sorted(set([sanitize(t) for t in templ]))[0:3])})
    except IOError as ioerr:
        print('File error: ' + str(ioerr))
        return(None)
    
james = get_coach_data('james2.txt')
julie = get_coach_data('julie2.txt')
mikey = get_coach_data('mikey2.txt')
sarah = get_coach_data('sarah2.txt')

print(james['Name'] + "'s fastest times are: " + james['Times'])
print(julie['Name'] + "'s fastest times are: " + julie['Times'])
print(mikey['Name'] + "'s fastest times are: " + mikey['Times'])
print(sarah['Name'] + "'s fastest times are: " + sarah['Times'])

 上面代码中用{}定义了一个map类型的数据结构，key分别是name,DOB,Times。

也可以用其它方式实现，类似于JAVA中的JAVABEAN

def sanitize(time_string):
    if '-' in time_string:
        splitter = '-'
    elif ':' in time_string:
        splitter = ':'
    else:
        return(time_string)
    (mins, secs) = time_string.split(splitter)
    return(mins + '.' + secs)

class AthleteList(list):

    def __init__(self, a_name, a_dob=None, a_times=[]):
        list.__init__([])
        self.name = a_name
        self.dob = a_dob
        self.extend(a_times)

    def top3(self):
        return(sorted(set([sanitize(t) for t in self]))[0:3])
        
def get_coach_data(filename):
    try:
        with open(filename) as f:
            data = f.readline()
        templ = data.strip().split(',')
        return(AthleteList(templ.pop(0), templ.pop(0), templ))
    except IOError as ioerr:
        print('File error: ' + str(ioerr))
        return(None)
    
james = get_coach_data('james2.txt')
julie = get_coach_data('julie2.txt')
mikey = get_coach_data('mikey2.txt')
sarah = get_coach_data('sarah2.txt')

print(james.name + "'s fastest times are: " + str(james.top3()))
print(julie.name + "'s fastest times are: " + str(julie.top3()))
print(mikey.name + "'s fastest times are: " + str(mikey.top3()))
print(sarah.name + "'s fastest times are: " + str(sarah.top3()))

注意class中的每个方法的第一个参数必须是self