Python - 为类创建多个对象

时间:2016-10-18 16:57:00

标签: python class object object-oriented-analysis

在python中我需要创建43个类的实例'学生'包括变量first_name,middle_name,last_name,student_id,通过读取文件(Students.txt)并解析它。文本文件如下所示:

Last Name  Midle Name  First Name   Student ID  
----------------------------------------------
Howard                  Moe         howar1m     
Howard                  Curly       howar1c     
Fine                    Lary        fine1l      
Howard                  Shemp       howar1s     
Besser                  Joe         besse1j     
DeRita      Joe         Curly       derit1cj    
Tiure       Desilijic   Jaba        tiure1jd    
Tharen                  Bria        thare1b     
Tai         Besadii     Durga       tai1db      
Hego                    Damask      hego1d      
Lannister               Tyrion      lanni1t     
Stark                   Arya        stark1a     
Clegane                 Sandor      clega1s     
Targaryen               Daenerys    targa1d     
Bombadil                Tom         bomba1t     
Brandybuck              Meriadoc    brand1m     
Took                    Pregrin     took1p      
McCoy                   Leonard     mccoy1l     
Scott                   Montgomery  scott1m     
Crusher                 Wesley      crush1w     
Montoya                 Inigo       monto1i     
Rugen                   Tyrone      rugen1t     
Solo                    Han         solo1h      
Corey                   Carl        corey1c     
Flaumel                 Evelyn      flaum1e     
Taltos                  Vlad        talto1v     
e'Drien                 Morrolan    edrie1m     
Watson                  John        watso1j     
McCoy                   Ebenezar    mccoy1e     
Carpenter               Molly       carpe1m     
Graystone               Zoe         grays1z
Adama                   William     adama1w
Adama       Joseph      Leland      adama1l
Roslin                  Laura       rosli1l
Baltar                  Gaius       balta1g
Tigh                    Ellen       tigh1e
Tigh                    Saul        tigh1s
Cottle                  Sherman     cottl1s
Zarek                   Thomas      zarek1t
Murphy      James       Alexander   murph1a
Sobchak                 Walter      sobch1w
Dane                    Alexander   dane1a
Gruber                  Hans        grube1h
Biggs       John        Gil         biggs1gj

班级学生是:

class Student (object):
    def __init__(self, first_name, middle_name, last_name, student_id):
        self.__first_name = first_name
        self.__middle_name = middle_name
        self.__last_name = last_name
        self.__student_id = student_id

最简单的阅读方式是什么?Students.txt'并创建学生的每个实例?

2 个答案:

答案 0 :(得分:1)

分步教程

要阅读文件内容,请使用io.open。如果任何名称具有突出的字符,请不要忘记指定文件编码。

with io.open('students.txt', mode="r", encoding="utf8") as fd:
    content = fd.read()

在这里,您阅读整个内容并将其存储在内存中(数据量很小)。您也可以使用迭代器。

然后,您可以使用str.splitlines()

逐行拆分内容
lines = content.splitlines()
# print(lines)

你会得到类似的东西:

['Last Name  Midle Name  First Name   Student ID  ',
 '----------------------------------------------',
 'Howard                  Moe         howar1m     ',
 'Howard                  Curly       howar1c     ',
 'Fine                    Lary        fine1l      ',
 'Howard                  Shemp       howar1s     ',
 'Besser                  Joe         besse1j     ',
 'DeRita      Joe         Curly       derit1cj    ',
 'Tiure       Desilijic   Jaba        tiure1jd    ',
 'Tharen                  Bria        thare1b     ']

您有(几乎)固定长度的线条,因此您可以使用切片来提取字段。

以下是您可以为标题执行的操作:

header = lines.pop(0)
fields = header[0:8], header[11:21], header[23:33], header[36:46]
# print(fields)

你得到:

('Last Nam', 'Midle Name', 'First Name', 'Student ID')

您可以删除连字符行:

lines.pop(0)

对于每一行,您也可以使用切片提取值。注意:切片索引略有不同:

for line in lines:
    record = line[0:8], line[12:21], line[23:34], line[36:46]
    # print(record)

您将获得具有尾随空格的值:

('Howard  ', '         ', ' Moe       ', 'howar1m   ')
('Howard  ', '         ', ' Curly     ', 'howar1c   ')
('Fine    ', '         ', ' Lary      ', 'fine1l    ')
('Howard  ', '         ', ' Shemp     ', 'howar1s   ')
('Besser  ', '         ', ' Joe       ', 'besse1j   ')
('DeRita  ', 'Joe      ', ' Curly     ', 'derit1cj  ')
('Tiure   ', 'Desilijic', ' Jaba      ', 'tiure1jd  ')
('Tharen  ', '         ', ' Bria      ', 'thare1b   ')

要避免尾随空格,请使用str.strip()函数:

for line in lines:
    record = line[0:8], line[12:21], line[23:34], line[36:46]
    record = [v.strip() for v in record]
    # print(record)

你得到:

['Howard', '', 'Moe', 'howar1m']
['Howard', '', 'Curly', 'howar1c']
['Fine', '', 'Lary', 'fine1l']
['Howard', '', 'Shemp', 'howar1s']
['Besser', '', 'Joe', 'besse1j']
['DeRita', 'Joe', 'Curly', 'derit1cj']
['Tiure', 'Desilijic', 'Jaba', 'tiure1jd']
['Tharen', '', 'Bria', 'thare1b']

此时,我建议您将记录存储为列表中的dict

records = []
for line in lines:
    record = line[0:8], line[12:21], line[23:34], line[36:46]
    record = [v.strip() for v in record]
    records.append(dict(zip(header, record)))

你得到:

[{'First Name': 'Moe', 'Last Nam': 'Howard', 'Midle Name': '', 'Student ID': 'howar1m'},
 {'First Name': 'Curly', 'Last Nam': 'Howard', 'Midle Name': '', 'Student ID': 'howar1c'},
 {'First Name': 'Lary', 'Last Nam': 'Fine', 'Midle Name': '', 'Student ID': 'fine1l'},
 {'First Name': 'Shemp', 'Last Nam': 'Howard', 'Midle Name': '', 'Student ID': 'howar1s'},
 {'First Name': 'Joe', 'Last Nam': 'Besser', 'Midle Name': '', 'Student ID': 'besse1j'},
 {'First Name': 'Curly', 'Last Nam': 'DeRita', 'Midle Name': 'Joe', 'Student ID': 'derit1cj'},
 {'First Name': 'Jaba', 'Last Nam': 'Tiure', 'Midle Name': 'Desilijic', 'Student ID': 'tiure1jd'},
 {'First Name': 'Bria', 'Last Nam': 'Tharen', 'Midle Name': '', 'Student ID': 'thare1b'}]

但你也可以使用一个类:

class Student(object):
    def __init__(self, first_name, middle_name, last_name, student_id):
        self.first_name = first_name
        self.middle_name = middle_name
        self.last_name = last_name
        self.student_id = student_id

    def __repr__(self):
        fmt = "<Student('{first_name}', '{middle_name}', '{last_name}', '{student_id}')>"
        return fmt.format(first_name=self.first_name, middle_name=self.middle_name, last_name=self.last_name, student_id=self.student_id)

构建一份学生名单:

students = []
for line in lines:
    record = line[0:8], line[12:21], line[23:34], line[36:46]
    record = [v.strip() for v in record]
    students.append(Student(*record))

你得到:

[<Student('Howard', '', 'Moe', 'howar1m')>,
 <Student('Howard', '', 'Curly', 'howar1c')>,
 <Student('Fine', '', 'Lary', 'fine1l')>,
 <Student('Howard', '', 'Shemp', 'howar1s')>,
 <Student('Besser', '', 'Joe', 'besse1j')>,
 <Student('DeRita', 'Joe', 'Curly', 'derit1cj')>,
 <Student('Tiure', 'Desilijic', 'Jaba', 'tiure1jd')>,
 <Student('Tharen', '', 'Bria', 'thare1b')>]

答案 1 :(得分:0)

list_of_students = []
with open('students.txt') as f:
    for line in f:
        data = line.split()
        if len(data) == 3:
            firstname, lastname, id = data
            list_of_students.append(Student(firstname, '', lastname, id))
        elif len(data) == 4:
            list_of_students.append(Student(*data))
        else:
            raise ValueError

我并不完全是你的输入文件的布局,所以这里有一点处理来处理没有中间名的情况。