python学习笔记三

数据持久化

import os

from lcmnester import printList

os.chdir("F:\\book\\python\\headfirst python book&&code\\code\\chapter3")

try:
        man=[]
        other=[]
        data=open("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()

        print("Man saied:")
        printList(man,1,1)

        print("Other saied:")
        printList(other,1,1)
       
       
except IOError:
        print("file is missing")

try:
        man_out=open("data_out.txt","w")
        other_out=open("other_out.txt","w")
        #写到文件
        print(man,file=man_out)
        print(other,file=other_out)
except IOError:
        print("File Error")
finally:
        man_out.close()

        other_out.close()

 

 

python中所有数值型都是不可变的，大部分数据类型都是不可变的，一般的改变都是改变副本。  不变的原因是因为python中都是引用，如果原地改变，就有可能导致所有引用的地方受影响。

 

 

BIF:

locals()：//返回当前作用域的所有有效标识符

str()：//将对象转换为字符串

 

 

with  open(file) as data:

        code...

 

 

except IOError as err:

 

上下文管理协议

 

 

函数调用时，可以通过行参名=实参的方式来指定参数值，这样有多个缺省参数时，在调用时可以不用在意参数顺序

 

pickle可以将数据对象持久化，持久化调用dump方式，载入调用load，如果是文件那边读写都需要用二进制模式打开

 

import os
import pickle
from lcmnester import printList

os.chdir("F:\\book\\python\\headfirst python book&&code\\code\\chapter3")

try:
        man=[]
        other=[]
        with open("sketch.txt") as data:
                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

                print("Man saied:")
                printList(man,1,1)

                print("Other saied:")
                printList(other,1,1)
       
       
except IOError as err:
        print("file is missing"+str(err))


try:
        with open("data_out.txt","wb") as man_out,open("other_out.txt","wb") as other_out:
                #printList(man,out=man_out)
                #printList(other,out=other_out)
                pickle.dump(man,man_out)
                pickle.dump(other,other_out)
except IOError:
        print("File Error")


with open("data_out.txt","rb") as  read_file:
        man_say=pickle.load(read_file)

print(man_say)