深浅拷贝&文件操作

Posted 2021-02-15 wenxin1120

一.深浅拷贝

　　浅拷贝:拷贝第一层(顶级对象),或者说:父级对象

　　深拷贝:拷贝所有对象,顶级对象及其嵌套对象,或者说父级对象及其子对象

# 应该每次都拷贝一份（但由于小数据池，未拷贝）
v1 = ‘alex‘
import copy
v2 = copy.copy(v1)
print(id(v1),id(v2))     #同一地址    

练习1
impot copy
v1 = [1,2,3]
v2 = copy.copy(v1)   #浅拷贝
print(v1 == v2)  # True
print(v1 is v2)  # False
print(v1[0] is v2[0])  # True

练习2

 import copy
 v1 = [1,2,3,{"name":‘武沛齐‘,"numbers":[7,77,88]},4,5]
 v2 = copy.copy(v1)
 print(v1 is v2)       #False
 print(v1[0] is v2[0])  #True
 print(v1[3] is v2[3])  #True
 print(v1[3][‘name‘] is v2[3][‘name‘])    #True
 print(v1[3][‘numbers‘] is v2[3][‘numbers‘])   #True
 print(v1[3][‘numbers‘][1] is v2[3][‘numbers‘][1])   #True

 

练习3
import copy
v1 = [1,2,3,{‘k1‘:123,‘k2‘:456}]
v2 = copy.deepcopy(v1)
print(v1 == v2) # True
print(v1 is v2) # False
print(v1[0] is v2[0]) # True
print(v1[3] == v2[3]) # True
print(v1[3] is v2[3]) # False

练习四
 import copy v1 = [1,2,3,{"name":‘武沛齐‘,"numbers":[7,77,88]},4,5] v2 = copy.deepcopy(v1) print(v1 is v2)    #False print(v1[0] is v2[0])  #True print(v1[3] is v2[3])  #False print(v1[3][‘name‘] is v2[3][‘name‘])  #True print(v1[3][‘numbers‘] is v2[3][‘numbers‘])  #False print(v1[3][‘numbers‘][1] is v2[3][‘numbers‘][1])  #True

 

二.文件操作

1. 读取: r (read):只能读不能写,文件不存在就报错

 

#打开文件:
    object = open(‘某txt文件‘,mode = ‘r‘,encoding = ‘utf-8‘)

#读取内容:
    content = object.read()
    print(content)

#关闭内容:
    object.close()

　　2. 写入:w (write): 只能写不能读(先清空文件),文件不存在就新建

#打开文件:
    object = open(‘某个txt文件或要新建的文件‘,mode = ‘w‘,encoding = ‘utf-8‘)

#写内容:
    object.write(‘xxx‘)

#关闭文件:
    object.close()

　　3.追加; a (append): 只能追加不能读,不存在则新建

#打开文件:
    object = open (‘某个txt文件或要新建的文件‘,mode = ‘a‘,encoding = ‘utf-8‘)

#写内容:
    object.append()

#关闭文件
    object.close()

 

 

三.文件可读写:

　　1.可读可写

读取
#写入：根据光标的位置，从当前光标位置开始进行写入操作（可能会将其他的文字覆盖）

file_object = open(‘某个txt文件‘,mode=‘r+‘,encoding=‘utf-8‘)
file_object.seek(2) # 调整光标的位置(根据字节来调整)

#读取内容:
content = file_object.read()
print(content)
file_object.write(‘xxx‘)

#关闭文件:
file_object.close()

　　2.可读可写

object = open (‘某个txt文件‘,mode = ‘w+‘,encoding = ‘utf-8‘)
data = object.read()
print(data)

object.write(‘xxx‘)
object.seek(0)
data = object.read()
print(data)

file_object.close()

 

 

四.读写操作

　　1.读:

file_object = open(‘某个txt文件‘,mode=‘r‘,encoding=‘utf-8‘)
# 读取文件的所有内容到内存
    con = file_object.read()

#从当前光标所在的位置向后读取文件两个字符
    con = file_object.read(2)

# 读取文件的所有内容到内存，并按照每一行进行分割到列表中。
    data_list = file_object.readlines()

# 如果以后读取一个特别大的文件 (**********)
    for line in file_object: 
         line = line.strip()  # strip : 去除换行(
)
         print(line)     #一行一行进行读取

 

　　2.写:

file_object = open(‘log.txt‘,mode=‘w‘,encoding=‘utf-8‘)
file_object.write(‘asdfadsfasdf
‘)
file_object.write(‘asdfasdfasdfsadf‘)
file_object.close()

 

 

五.练习:

　　1.请将user中的元素根据 _ 链接，并写入 ‘a1.txt‘ 的文件

    user = [‘alex‘,‘eric‘]
    data = ‘_‘.join(user)
    object = open(‘a1.txt‘,mode = ‘w‘,encoding = ‘utf-8‘)
    object.write(data)
    object.close()

　　2.请将user中的元素根据 | 链接，并写入 ‘a2.txt‘ 的文件

    user = [
    {‘name‘:‘alex‘,‘pwd‘:‘123‘},   
    {‘name‘:‘eric‘,‘pwd‘:‘olbody‘},]
    object = open(‘a2.txt‘,mode = ‘w‘,encoding = ‘utf-8‘)
    for item in user:
        line = ‘%s|%s
‘ %(item[‘name‘],item[‘pwd‘])
        object.write(line)
     object.close()

 

　　3.请将a2.(根据2)txt中的文件读取出来并添加到一个列表中 [‘alex|123‘,‘eric|olbody‘]

方法一:
    list = []
    objecct = open(‘a2.txt‘,mode = ‘r‘,encoding = ‘utf-8‘)
    for line in object:
       line = line.strip()
       list.append(line)
     print(list)
    
 方法二:
      file_obj = open(‘a2.txt‘,mode=‘r‘,encoding=‘utf-8‘)
    content = file_obj.read()
    file_obj.close()
    content = content.strip() #去除最后一个换行
    data_list = content.split(‘
‘) #根据中间的换行进行切割
    print(data_list)