python – How to open a file for both reading and writing?
python – How to open a file for both reading and writing?
Heres how you read a file, and then write to it (overwriting any existing data), without closing and reopening:
with open(filename, r+) as f:
data = f.read()
f.seek(0)
f.write(output)
f.truncate()
Summarize the I/O behaviors
| Mode | r | r+ | w | w+ | a | a+ |
|---|---|---|---|---|---|---|
| Read | + | + | + | + | ||
| Write | + | + | + | + | + | |
| Create | + | + | + | + | ||
| Cover | + | + | ||||
| Point in the beginning | + | + | + | + | ||
| Point in the end | + | + |
and the decision branch
python – How to open a file for both reading and writing?
r+ is the canonical mode for reading and writing at the same time. This is not different from using the fopen() system call since file() / open() is just a tiny wrapper around this operating system call.