How to Properly Redirect Python Print Output to a Text File?

Redirect Python Output to Text File

When attempting to redirect print output to a text file using Python, you may encounter difficulties if your chosen method doesn't produce the desired results.

Problem Description

The following code fails to redirect output to a file using sys.stdout:

f = open('output.txt','w')
sys.stdout = f

path= '/home/xxx/nearline/bamfiles'
bamfiles = glob.glob(path + '/*.bam')

for bamfile in bamfiles:
    filename = bamfile.split('/')[-1]
    print 'Filename:', filename

Solution

Instead of sys.stdout, consider using a file object for printing:

with open('out.txt', 'w') as f:
    print('Filename:', filename, file=f)  # Python 3.x

Alternative Solutions

• Use a context manager to redirect output:

from contextlib import redirect_stdout

with open('out.txt', 'w') as f:
    with redirect_stdout(f):
        print('data')

• Redirect output externally from the shell:

./script.py > out.txt

Additional Considerations

• Ensure that the glob function is locating the intended files.
• Properly manipulate file paths using os.path.join and os.path.basename.

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