Writing to Text Files

You can write to files in much the same way that you read from them. First you open a file and get a stream object, then you use methods on the stream object to write data to the file, then you close the file.

To open a file for writing, use the open() function and specify the write mode. There are two file modes for writing:

• Write” mode will overwrite the file. Pass mode='w' to the open() function.
• “Append” mode will add data to the end of the file. Pass mode='a' to the open() function.

Either mode will create the file automatically if it doesn’t already exist, so there’s never a need for any sort of fiddly “if the file doesn’t exist yet, create a new empty file just so you can open it for the first time” function. Just open a file and start writing.

Just open a file and start writing.

You should always close a file as soon as you’re done writing to it, to release the file handle and ensure that the data is actually written to disk. As with reading data from a file, you can call the stream object’s close() method, or you can use the with statement and let Python close the file for you. I bet you can guess which technique I recommend.