Python读写文件的方法，及其读写（IO）的几种模式，

Python File Modes Description
原网址见：https://www.programiz.com/python-programming/file-operation

‘r’ ： Open a file for reading. (default默认)
‘w’：Open a file for writing. Creates a new file if it does not exist or truncates the file if it exists.
‘x’ ：Open a file for exclusive creation. If the file already exists, the operation fails.
‘a’ ： Open for appending at the end of the file without truncating it. Creates a new file if it does not exist.
‘t’ ： Open in text mode. (default默认)
‘b’ ： Open in binary mode.
‘+’ ： Open a file for updating (reading and writing)

示例：

f = open("test.txt")      # equivalent to 'r' or 'rt'
f = open("test.txt",'w')  # write in text mode
f = open("lalala",'r+') # read and write
f = open("img.bmp",'r+b') # read and write in binary mode

读出来并且删除特定的一行后写回去：

f = open("target.txt","r+")
d = f.readlines()
f.seek(0)
for i in d:
    if i != "line you want to remove...":
        f.write(i)
f.truncate()
f.close()

另外一种实现的方式（用了两个循环，但更容易读明白）：

#把所有的行读出来（其实是存到了一个list列表中）：
f = open("yourfile.txt","r")
lines = f.readlines()
f.close() 

#重新打开，并写回去：
f = open("yourfile.txt","w")

for line in lines:
  if line!="nickname_to_delete"+"\n":
    f.write(line)
f.close()

这两种方法的原网址：https://stackoverflow.com/questions/4710067/deleting-a-specific-line-in-a-file-python