Head First Python-Python中与文件相关的操作-读、处理、写

最近在看head first python，前面也写了一些笔记，但是基本上没有涉及到一些完整的代码，现在将书中的文件相关操作的代码整理，供以后参考。

主要分为两大部分，读取文件、处理异常，处理文件、存储文件。

0，处理文件

首先介绍后面将会用到的知识点，格式化输出列表;

如果一个列表嵌套多层列表，使用一般的方法来打印无法打印出嵌套的列表。下面的方法只能打印出一层，如果想打印多层怎么办？

movies=['aWith a ','bpopulation of 1060', ['cthe village','dis carpeted with ','eazalea blossoms', ['fwith fast-flowing rivers ','gscattered guesthouses','hadding strokes and splashes to ','ithe natural canvas.']]]

print(movies)

def printList(movies):

    for i in movies:

        print(i)

print(printList(movies))

下面通过给printList增加参数来控制格式化输出（intent控制是否需要格式化，t用来控制指标表符个数）：

movies=['aWith a ','bpopulation of 1060', ['cthe village','dis carpeted with ','eazalea blossoms', ['fwith fast-flowing rivers ','gscattered guesthouses','hadding strokes and splashes to ','ithe natural canvas.']]]

print(movies)#1

def printList(movies,intent=False,t=0):

    for i in movies:

        if isinstance(i , list): #isinstance检查一个标识符是否指示某个指定类型的数据对象

           # for j in i:

                printList(i,intent,t+1)#增加一层嵌套制表符加1

        else:

            if intent:

                for j in range(t):

                    print("\t", end='')

            print(i)

print(printList(movies,False))#2

print(printList(movies,True,0))#3

输出如下：

1，读取文件

pyhont中使用open来打开一个文件：

import  os

if os.path.exists('./temp/sketch.txt'):

    data =open('./temp/sketch.txt')

    print(data.readline(),end='')

    print(data.readline(),end='')

    data.seek(0)

    for each_line in data:

        if not each_line.find(':') == -1:

            (role,line_spoken)=each_line.split(':',1)

            print(role,end='')

            print(' said: ',end='')

            print(line_spoken,end='')

    data.close()

else:

    print('file not exists!!!')

2，处理异常

如果要读取的文件不存在咋办？

data =open('./temp/sketch.txt')

print(data.readline(),end='')

print(data.readline(),end='')

data.seek(0)

for each_line in data:

    try:

        (role,line_spoken)=each_line.split(':',1)

        print(role,end='')

        print(' said: ',end='')

        print(line_spoken,end='')

    except ValueError:

        pass

data.close()

我们知道，打开一个文件，读取或者写入结束后要进行关闭。

3，存储文件

保存一个文件：

（1）使用print（），print函数的参数file来定义输出对象，默认输出到屏幕：

man = []

other = []

try:

    data=open('./data/sketch.txt')

    for each_line in data:

        try:

            (role,line_spoken)=each_line.split(':',1)

            line_spoken=line_spoken.strip()

            if role=='Man':

                man.append(line_spoken)

            elif role=='Other Man':

                other.append(line_spoken)

        except ValueError:

            pass

    data.close()

except IOError as err:

    print("the datafile is missing..."+str(err))

try:

    with open('./temp/man_data.txt','a') as man_data:

        print(man, file=man_data)

    with open('./temp/other_data.txt','a') as other_data:

        print(other, file=other_data)

except IOError as err:

    print ('ERROR: '+str(err))

（2）使用pickle（），pickle函数有存文件dump()和读文件load()两个方法，将文件以二进制流的形式存储到本地：

import pickle

import sys

def print_lol(the_list,indent=False,level=0,lol=sys.stdout):

    for each_item in the_list:

        if isinstance(each_item,list):

            print_lol(each_item,indent,level+1,lol)

        else:

            if  indent:

                for tab_stop in range(level):

                    print('\t',end='',file=lol)

            print(each_item,file=lol)

man = []

other = []

try:

    data=open('./data/sketch.txt')

    for each_line in data:

        try:

            (role,line_spoken)=each_line.split(':',1)

            line_spoken=line_spoken.strip()

            if role=='Man':

                man.append(line_spoken)

            elif role=='Other Man':

                other.append(line_spoken)

        except ValueError:

            pass

    data.close()

except IOError as err:

    print("the datafile is missing..."+str(err))

#存文件

try:

    with open('./temp/man_data.dat','wb') as man_data:

        pickle.dump(man,man_data)

    with open('./temp/other_data.dat','wb') as other_data:

        pickle.dump(other,other_data)

except pickle.PickleError as err:

    print ('ERROR: '+str(err))

#读文件

new_man=[]

try:

    with open('./temp/man_data.dat','rb') as new_man_file:

        new_man=pickle.load(new_man_file)

except IOError as err:

    print('IOError: '+str(err))

except pickle.PickleError as perr:

    print('PickError: '+ str(perr))

print_lol(new_man)

print(new_man[0])

print(new_man[-1])

代码来源：head first python

巴特西

Head First Python-Python中与文件相关的操作-读、处理、写

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