python基础知识学习（文件操作）

╰半橙微兮° 2023-03-01 06:10 17阅读 0赞

## 文件操作 ##

**打开、读写、关闭**

1.  **open**(filename, mode=‘r/w/a…’, buf = -1, encoding=‘GBK /utf8…’ …)  
    打开成功：返回**可迭代对象**  
    打开失败：抛出异常
2.  filename.**close()**
3.  **with**关键字：with open( ) as fp  
    eg.

with open('test.txt','r') as src, open('test_new.txt', 'w') as dst:
    dst.write(src.read())	#【write() 只能写入字符串】不用关闭

fp = open(r'E:\python_learn\test.txt', 'r')
    print(fp.read())
    fp.close() # 需要关闭

fp = open(r'E:\python_learn\test.txt', 'r')
    lst = list()
    for line in fp:		#【一行一行读取数据】
    	lst.append(int(line))

**二进制文件操作：对文件进行序列化**  
①**pickle模块**：import pickle  
写文件

with open(r'E:\python_learn\sample_pickle.dat', 'wb') as f:
    	try:
    		pickle.dump(len(data), f) //data为一个列表，写入列表长度
    		for item in data:
    			pickle.dump(item, f) //写入列表中的数据
    	except:
    		print('写文件异常！')

读文件

with open(r'E:\python_learn\sample_pickle.dat', 'rb') as f:
    	n = pickle.load(f) //读出文件长度
    	for i in range(n):
    		x = pickle.load(f) //读出文件内容
    		print(x)

②struct模块：
    写文件

import struct
    n = 130000000
    x = 96.45
    b = True
    s = 'al@中国'
    sn = struct.pack('if?', n , x, b) //序列化
    with open(r'E:\python_learn\sample_pickle.dat', 'wb') as f:
    	f.write(sn)	//9个字节
    	f.write(s.encode()) //9个字节

读文件：

with open(r'E:\python_learn\sample_pickle.dat', 'rb') as f:
    	sn = f.read(9)	//读9个字节
    	tu = struct.unpack('if?',sn)	//反序列化，得到一个元组
    	print(tu)
    	n, x, bl = tu	//序列解包
    	print(n, x, bl)
    	s = f.read(9).decode()	//读9个字节
    	print(s)

③shelve模块：
    写文件

with shelve.open(r'E:\python_learn\sample_shelve.dat') as fp: //文件自动生成，原来没有这个文件，否则报错
    	fp['zhangsan'] = zhangsan
    	fp['lisi'] = lisi
    	for i in range(5):
    		fp[str(i)] = str(i)

读文件

with shelve.open(r'E:\python_learn\sample_shelve.dat') as fp:
    	print(fp['zhangsan'])
    	print(fp['zhangsan']['age'])
    	print(fp['lisi']['qq'])
    	print(fp['3'])

④marshal模块：和pickle用法相似  
写文件

with open(r'E:\python_learn\sample_marshal.dat', 'wb') as fp:
    	marshal.dump(len(x), fp)	//写对象个数
    	for item in x:
    		marshal.dump(item, fp)

读文件

with open(r'E:\python_learn\sample_marshal.dat', 'rb') as fp:
    	n = marshal.load(fp)	//读对象个数
    	for i in range(n):
    		print(marshal.load(fp))