了解在 Python 中连接文件的代码？

Question

I need to concatenate a few large files in Python, and came across a helpful snippet of code here, but am having trouble understanding a small part of it. Here is the code:

filenames = ['file1.txt', 'file2.txt', ...]
     with open('path/to/output/file', 'w') as outfile:
          for fname in filenames:
               with open(fname) as infile:
                    for line in infile:
                         outfile.write(line)

The only thing I don't understand is what the 'w' is supposed to represent, so it would be great if someone explained it. Thanks!

Answer 1

When you open a file, you must specify a mode in which it will be opened. The character 'w' stands for 'write', and it means that the file will be opened for writing, after it has been truncated.

Subsequent calls to open() in your code snippet ( with open(fname) as infile ) need not explicitly define a mode, since 'r' (which stands for 'read') is the default mode used when calling open() . They are equivalent to writing:

with open(fname, 'r') as infile:
    # rest of code here

See the documentation for open for more details.