"Go" python File open in detail--a, A +, r+, w+ differences

Original address: http://blog.csdn.net/ztf312/article/details/47259805

The first step to exclude file open mode error:

R Read-only , r+ read/write, not created

W New write-only , w+ New Read-write , both will clear the contents of the file

(opens in W mode and cannot be read out.) w+ Readable and writable)

the difference between **w+ and r+ :

r+: Readable and writable, if the file does not exist, error; w+: Readable and writable, if the file does not exist, create

the difference between r+ and A + :

FD = open ("1.txt",'w+') Fd.write ('123') FD= Open ("1.txt",'r+') Fd.write ('456') FD= Open ("1.txt",'A +') Fd.write ('789')

Results: 456789

Description r+ the overwrite write.

Open the file in a a,a+ way, attach it

(a: additional write mode open, unreadable; a+: additional read and write mode open)

Open the file with the ' U ' flag, and all the line separators are returned with a newline character (such as read* ()) by means of the Python input method (example # ()). (' RU ' mode also supports ' RB ' option).

R and u require that the file must exist

non-readable open mode :W and a

How to open a new file if it does not exist: a,a+,w,w+

>>> Fd=open (r'f:\mypython\test.py','W')#Read -only mode open, read error>>>Fd.read () Traceback (most recent): File"<stdin>", Line 1,inch<module>Ioerror:file notOpen forReading>>> Fd=open (r'f:\mypython\test.py','a')#additional write mode open, read error>>>Fd.read () Traceback (most recent): File"<stdin>", Line 1,inch<module>Ioerror:file notOpen forReading>>></span></span></span>

"Go" python File open in detail--a, A +, r+, w+ differences