I am using the below statements to redirect the output of python program to a log_file and it works.
import sys
sys.stdout = open(log_file, 'a', buffering=1)
But, I would like to pass one or two specific print statements to another flat file(let's suppose sample_file.txt). How can I do that ?
On older Python's, you can use the 'chevron print' form of the print statement to print from a specific print statement to a file:
Python 2.7.13 (default, Dec 19 2016, 07:22:39)
[GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.42.1)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> f=open('/tmp/file.txt','a')
>>> print "hello"
hello
>>> print >>f, 'hello'
>>> f.close()
>>> open('/tmp/file.txt').read()
'hello\n'
The form print >>fh prints what follows to the file handle fh
Or import the print function in Python 2 to get the ability to add a file handle to the print.
If you are using python3, you can optionally pass a fileobject to your print function. Like this:
>>> f = open('sample_file.txt', 'w')
>>> print("hello", file = f)
>>> print("hello1", file = f)
>>> print("hello2", file = f)
>>> f.close()
Or, even better, use context manager.
>>> with open('etc.txt','w') as f:
... print("hello", file = f)
... print("hello2", file = f)
... print("hello2", file = f)
In python2, you can use this feature as well. But you need to import the print() function from python3. Add this import statement.
from __future__ import print_function
from __future__ import print_function among the imports of your file.Assuming you wanted to append new lines to an existing text file, you could modify your code as such, quite simply:
import sys
sys.stdout = open(log_file, 'a', buffering=1)
with open("sample_file.txt", "a") as f:
f.write("line 1\n")
f.write("line 2\n")
Note that the file "sample_file.txt" will be edited in whatever folder/directory the Python file is run in, unless you change it to specify a full (or relative) path.
sys.stdout = open('/opt/test/test_user/data/PLANNING_%s_%s_%s.etab' % (type, period, self.now), 'a', buffering=1) with open('/opt/test/test_user/data/SUB_PLANNING_%s_%s_%s.etab'' % (type, period, self.now), 'a') as e: SyntaxError: invalid syntax
print rather than write, especially as the question says they wish to "print statements to another file"Elegant solution would be using a context manager in the following manner
print("hello") # Prints to the console
with log_to_file(sys, LOG_FILE_PATH):
print("hello") # Prints to the file
print("hello") # Prints to the console
To build this context manager will be using the following code
from contextlib import contextmanager
import sys
@contextmanager
def log_to_file(sys, LOG_FILE_PATH):
log_file = open(LOG_FILE_PATH, 'a')
sys.stdout = log_file
yield
log_file.close()
sys.stdout = sys.__stdout__
Now you can decide where to write every time simply by passing a different file path and your code will be clean and Pythonic
append modeand write your data in it:with open("sample_file.txt", "a") as f: f.write("hello world!\n")loggingmodule in your project.