day-2 python 文件讀寫模式r,r+,w,w+,a,a+的區別

r+和w+都是可讀可寫，區別在於r+讀文件時，不會覆蓋之前的內容，之前的內容能夠讀出來；w+讀時，會覆蓋之前的內容；所以讀文件時，用r或者r+

#讀操作 r

filepath = 'aa.log' #aa.log存在
#讀操作
#read()方法，一次都讀出來
with open(filepath,'r') as f:
    print(f.read())

C:\Users\admin\Miniconda3\python.exe E:/python/文件讀寫.py
hello world!


Process finished with exit code 0

filepath = 'a.log'  #a.log不存在，執行報錯
#讀操作
#read()方法，一次都讀出來
with open(filepath,'r') as f:
    print(f.read())

C:\Users\admin\Miniconda3\python.exe E:/python/文件讀寫.py
Traceback (most recent call last):
  File "E:/python/文件讀寫.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

 

#讀寫操作 r+

#r+寫操作
filepath = 'aa.log'
with open(filepath, 'r+') as f:
    f.write('文字被替換成hahaha')
    print(f.read())

C:\Users\admin\Miniconda3\python.exe E:/python/文件讀寫.py
被替換成hahaha

Process finished with exit code 0

#readline()讀操作

filepath = 'my.log'
with open(filepath,'r',encoding='UTF-8') as f:
    print(f.readline().strip())
    print(f.readline().strip())

C:\Users\admin\Miniconda3\python.exe E:/python/文件讀寫.py
2019-10-12 09:34:23,073 - E:/python/test.py[line:9] - DEBUG: 默認日志級別是debug
2019-10-12 09:34:23,075 - E:/python/test.py[line:10] - INFO: info級別

Process finished with exit code 0

#readlines()讀操作,讀到的內容，返回一個列表

#readlines()方法，一次都讀出來，並返回一個列表
with open(filepath,'r',encoding='UTF-8') as f:
    print(f.readlines())

C:\Users\admin\Miniconda3\python.exe E:/python/文件讀寫.py
['2019-10-12 默認日志級別是debug\n', '2019-10-12 info級別\n', '\n']

Process finished with exit code 0

#將readlines讀到的內容存放到line中，使用for循環遍歷內容
with open(filepath,'r',encoding='UTF-8') as f:
    lines = f.readlines()
for line in lines:
    print(line.strip())

C:\Users\admin\Miniconda3\python.exe E:/python/文件讀寫.py
2019-10-12 默認日志級別是debug
2019-10-12 info級別


Process finished with exit code 0

 

# 如果要逐行讀取，直接遍歷文件對象就可以了
with open(filepath,'r',encoding='UTF-8') as f:
    for line in f:
        print(line.strip())

C:\Users\admin\Miniconda3\python.exe E:/python/文件讀寫.py
2019-10-12 默認日志級別是debug
2019-10-12 info級別


Process finished with exit code 0

 

#寫操作
with open(filepath,'w',encoding='UTF-8') as f:
    f.write('hello world!\n')

with open(filepath,'r',encoding='UTF-8') as f:
    print(f.read())

C:\Users\admin\Miniconda3\python.exe E:/python/文件讀寫.py
hello world!


Process finished with exit code 0

#w+讀寫模式

with open(filepath,'w+',encoding='UTF-8') as f:
    f.write('hello world!\n')
    f.seek(0)
    print(f.read())

C:\Users\admin\Miniconda3\python.exe E:/python/文件讀寫.py
hello world!


Process finished with exit code 0

#a+追加讀寫

with open(filepath,'a+',encoding='UTF-8') as f:
    f.write('hello world!\n')
    f.seek(0)
    print(f.read())

C:\Users\admin\Miniconda3\python.exe E:/python/文件讀寫.py
hello world!
hello world!


Process finished with exit code 0

 

#讀模式，只能讀，不能寫，默認讀模式
f = open(r'E:\cnz\day1\列表.py','r',encoding='utf-8')
result = f.read()
print(result)
f.close()

#讀模式r 寫模式w 追加模式a
#寫模式，只能寫，不能讀，寫模式會覆蓋之前的內容

f = open('test.txt','w',encoding='utf-8')
f.write('abc')
f.close()

# 追加模式，寫文件時，不會覆蓋之前的內容
f = open('test.txt','a',encoding='utf-8')
# f.write('哈哈哈')
f.read()
f.close()

# 總結：
# 讀模式，只能讀，不能寫，打開不存在的文件會報錯
# 寫模式，只能寫，不能讀，打開不存在的文件會創建
# 追加模式，只能寫，不能讀，在原文件基礎上增加內容，打開不存在的文件，會創建
# 只要跟r有關的，打開不存在的文件，會報錯
# 只要和w有關，都會清空之前的文件
# a+模式，文件指針模式是在末尾的，如果想讀文件，需要seek(0)
#writelines傳一個list，會把list里面的元素寫到文件里

# r+       w+       a+
# 讀寫模式  寫讀模式  追加讀模式

f = open('test3.txt','a+',encoding='utf-8')
f.write('哈哈哈1')
f.read()
f.close()

l = ['a','b','c','d']
f = open('test.txt','w',encoding='utf-8')
f.writelines(l)
f.close()