Python Language Files & Folders I/O File modes
Example
There are different modes you can open a file with, specified by the mode parameter. These include:
-
'r'- reading mode. The default. It allows you only to read the file, not to modify it. When using this mode the file must exist. -
'w'- writing mode. It will create a new file if it does not exist, otherwise will erase the file and allow you to write to it. -
'a'- append mode. It will write data to the end of the file. It does not erase the file, and the file must exist for this mode. -
'rb'- reading mode in binary. This is similar torexcept that the reading is forced in binary mode. This is also a default choice. -
'r+'- reading mode plus writing mode at the same time. This allows you to read and write into files at the same time without having to userandw. -
'rb+'- reading and writing mode in binary. The same asr+except the data is in binary -
'wb'- writing mode in binary. The same aswexcept the data is in binary. -
'w+'- writing and reading mode. The exact same asr+but if the file does not exist, a new one is made. Otherwise, the file is overwritten. -
'wb+'- writing and reading mode in binary mode. The same asw+but the data is in binary. -
'ab'- appending in binary mode. Similar toaexcept that the data is in binary. -
'a+'- appending and reading mode. Similar tow+as it will create a new file if the file does not exist. Otherwise, the file pointer is at the end of the file if it exists. -
'ab+'- appending and reading mode in binary. The same asa+except that the data is in binary.with open(filename, 'r') as f: f.read() with open(filename, 'w') as f: f.write(filedata) with open(filename, 'a') as f: f.write('\n' + newdata)
| r | r+ | w | w+ | a | a+ | |
|---|---|---|---|---|---|---|
| Read | ✔ | ✔ | ✘ | ✔ | ✘ | ✔ |
| Write | ✘ | ✔ | ✔ | ✔ | ✔ | ✔ |
| Creates file | ✘ | ✘ | ✔ | ✔ | ✔ | ✔ |
| Erases file | ✘ | ✘ | ✔ | ✔ | ✘ | ✘ |
| Initial position | Start | Start | Start | Start | End | End |
Python 3 added a new mode for exclusive creation so that you will not accidentally truncate or overwrite and existing file.
'x'- open for exclusive creation, will raiseFileExistsErrorif the file already exists'xb'- open for exclusive creation writing mode in binary. The same asxexcept the data is in binary.'x+'- reading and writing mode. Similar tow+as it will create a new file if the file does not exist. Otherwise, will raiseFileExistsError.'xb+'- writing and reading mode. The exact same asx+but the data is binary
| x | x+ | |
|---|---|---|
| Read | ✘ | ✔ |
| Write | ✔ | ✔ |
| Creates file | ✔ | ✔ |
| Erases file | ✘ | ✘ |
| Initial position | Start | Start |
Allow one to write your file open code in a more pythonic manner:
Python 3.x3.3
try:
with open("fname", "r") as fout:
# Work with your open file
except FileExistsError:
# Your error handling goes here
In Python 2 you would have done something like
Python 2.x2.0
import os.path
if os.path.isfile(fname):
with open("fname", "w") as fout:
# Work with your open file
else:
# Your error handling goes here
