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
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