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("	", 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('	',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