day-2 python 文件读写模式r,r+,w,w+,a,a+的区别
r+和w+都是可读可写,区别在于r+读文件时,不会覆盖之前的内容,之前的内容能够读出来;w+读时,会覆盖之前的内容;所以读文件时,用r或者r+
#读操作 r
1 filepath = 'aa.log' #aa.log存在 2 #读操作 3 #read()方法,一次都读出来 4 with open(filepath,'r') as f: 5 print(f.read())
C:\Users\admin\Miniconda3\python.exe E:/python/文件读写.py
hello world!
Process finished with exit code 0
1 filepath = 'a.log' #a.log不存在,执行报错 2 #读操作 3 #read()方法,一次都读出来 4 with open(filepath,'r') as f: 5 print(f.read())
C:\Users\admin\Miniconda3\python.exe E:/python/文件读写.py Traceback (most recent call last): File "E:/python/文件读写.py", line 4, in <module> with open(filepath,'r') as f: FileNotFoundError: [Errno 2] No such file or directory: 'a.log' Process finished with exit code 1
#读写操作 r+
1 #r+写操作 2 filepath = 'aa.log' 3 with open(filepath, 'r+') as f: 4 f.write('文字被替换成hahaha') 5 print(f.read())
C:\Users\admin\Miniconda3\python.exe E:/python/文件读写.py
被替换成hahaha
Process finished with exit code 0
#readline()读操作
1 filepath = 'my.log' 2 with open(filepath,'r',encoding='UTF-8') as f: 3 print(f.readline().strip()) 4 print(f.readline().strip())
C:\Users\admin\Miniconda3\python.exe E:/python/文件读写.py 2019-10-12 09:34:23,073 - E:/python/test.py[line:9] - DEBUG: 默认日志级别是debug 2019-10-12 09:34:23,075 - E:/python/test.py[line:10] - INFO: info级别 Process finished with exit code 0
#readlines()读操作,读到的内容,返回一个列表
1 #readlines()方法,一次都读出来,并返回一个列表 2 with open(filepath,'r',encoding='UTF-8') as f: 3 print(f.readlines())
C:\Users\admin\Miniconda3\python.exe E:/python/文件读写.py ['2019-10-12 默认日志级别是debug\n', '2019-10-12 info级别\n', '\n'] Process finished with exit code 0
1 #将readlines读到的内容存放到line中,使用for循环遍历内容 2 with open(filepath,'r',encoding='UTF-8') as f: 3 lines = f.readlines() 4 for line in lines: 5 print(line.strip())
C:\Users\admin\Miniconda3\python.exe E:/python/文件读写.py 2019-10-12 默认日志级别是debug 2019-10-12 info级别 Process finished with exit code 0
1 # 如果要逐行读取,直接遍历文件对象就可以了 2 with open(filepath,'r',encoding='UTF-8') as f: 3 for line in f: 4 print(line.strip())
C:\Users\admin\Miniconda3\python.exe E:/python/文件读写.py 2019-10-12 默认日志级别是debug 2019-10-12 info级别 Process finished with exit code 0
1 #写操作 2 with open(filepath,'w',encoding='UTF-8') as f: 3 f.write('hello world!\n') 4 5 with open(filepath,'r',encoding='UTF-8') as f: 6 print(f.read())
C:\Users\admin\Miniconda3\python.exe E:/python/文件读写.py
hello world!
Process finished with exit code 0
#w+读写模式
1 with open(filepath,'w+',encoding='UTF-8') as f: 2 f.write('hello world!\n') 3 f.seek(0) 4 print(f.read())
C:\Users\admin\Miniconda3\python.exe E:/python/文件读写.py
hello world!
Process finished with exit code 0
#a+追加读写
1 with open(filepath,'a+',encoding='UTF-8') as f: 2 f.write('hello world!\n') 3 f.seek(0) 4 print(f.read())
C:\Users\admin\Miniconda3\python.exe E:/python/文件读写.py
hello world!
hello world!
Process finished with exit code 0
1 #读模式,只能读,不能写,默认读模式 2 f = open(r'E:\cnz\day1\列表.py','r',encoding='utf-8') 3 result = f.read() 4 print(result) 5 f.close() 6 7 #读模式r 写模式w 追加模式a 8 #写模式,只能写,不能读,写模式会覆盖之前的内容 9 10 f = open('test.txt','w',encoding='utf-8') 11 f.write('abc') 12 f.close() 13 14 # 追加模式,写文件时,不会覆盖之前的内容 15 f = open('test.txt','a',encoding='utf-8') 16 # f.write('哈哈哈') 17 f.read() 18 f.close() 19 20 # 总结: 21 # 读模式,只能读,不能写,打开不存在的文件会报错 22 # 写模式,只能写,不能读,打开不存在的文件会创建 23 # 追加模式,只能写,不能读,在原文件基础上增加内容,打开不存在的文件,会创建 24 # 只要跟r有关的,打开不存在的文件,会报错 25 # 只要和w有关,都会清空之前的文件 26 # a+模式,文件指针模式是在末尾的,如果想读文件,需要seek(0) 27 #writelines传一个list,会把list里面的元素写到文件里 28 29 # r+ w+ a+ 30 # 读写模式 写读模式 追加读模式 31 32 f = open('test3.txt','a+',encoding='utf-8') 33 f.write('哈哈哈1') 34 f.read() 35 f.close() 36 37 l = ['a','b','c','d'] 38 f = open('test.txt','w',encoding='utf-8') 39 f.writelines(l) 40 f.close()