Python File Slurp
Question:
Is there a one-liner to read all the lines of a file in Python, rather than the standard:
f = open('x.txt')
cts = f.read()
f.close()
Seems like this is done so often that there’s got to be a one-liner. Any ideas?
Answers:
This will slurp the content into a single string in Python 2.61 and above:
with open('x.txt') as x: f = x.read()
And this will create a list of lines:
with open('x.txt') as x: f = x.readlines()
These approaches guarantee immediate closure of the input file right after the reading.
Footnote:
- This approach can also be used in Python 2.5 using
from __future__ import with_statement.
An older approach that does not guarantee immediate closure is to use this to create a single string:
f = open('x.txt').read()
And this to create a list of lines:
f = open('x.txt').readlines()
In practice it will be immediately closed in some versions of CPython, but closed “only when the garbage collector gets around to it” in Jython, IronPython, and probably some future version of CPython.
If you are on Python3, make sure you properly respect your file’s input encoding, e.g.:
import codecs
with codecs.open(filename, 'r', encoding="utf8") as file:
cts = file.read()
Find the list of codec names in the Python3 codec list.
(The mechanism is also advisable for Python2 whenever you expect any non-ASCII input)
Starting in Python 3.5, you can use the pathlib module for a more modern interface. Being Python 3, it makes a distinction between reading text and reading bytes:
from pathlib import Path
text_string = Path('x.txt').read_text() # type: str
byte_string = Path('x.txt').read_bytes() # type: bytes
Is there a one-liner to read all the lines of a file in Python, rather than the standard:
f = open('x.txt')
cts = f.read()
f.close()
Seems like this is done so often that there’s got to be a one-liner. Any ideas?
This will slurp the content into a single string in Python 2.61 and above:
with open('x.txt') as x: f = x.read()
And this will create a list of lines:
with open('x.txt') as x: f = x.readlines()
These approaches guarantee immediate closure of the input file right after the reading.
Footnote:
- This approach can also be used in Python 2.5 using
from __future__ import with_statement.
An older approach that does not guarantee immediate closure is to use this to create a single string:
f = open('x.txt').read()
And this to create a list of lines:
f = open('x.txt').readlines()
In practice it will be immediately closed in some versions of CPython, but closed “only when the garbage collector gets around to it” in Jython, IronPython, and probably some future version of CPython.
If you are on Python3, make sure you properly respect your file’s input encoding, e.g.:
import codecs
with codecs.open(filename, 'r', encoding="utf8") as file:
cts = file.read()
Find the list of codec names in the Python3 codec list.
(The mechanism is also advisable for Python2 whenever you expect any non-ASCII input)
Starting in Python 3.5, you can use the pathlib module for a more modern interface. Being Python 3, it makes a distinction between reading text and reading bytes:
from pathlib import Path
text_string = Path('x.txt').read_text() # type: str
byte_string = Path('x.txt').read_bytes() # type: bytes