You can use the $ notation for the last line to specify to the end of the file and double greater-than symbols (>>) after the w to indicate that you want to append to rather than overwrite the file.

对于最后一行，可以使用 $ 表示文件的末尾。 可以在 w 后面使用两个大于号（>>）表示希望把内容附加到文件中而不是覆盖文件。

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The next line creates a file object, passing in the name "testit.txt" and a 'w' character (to let you write to the file).

接下来的一行创建file对象，传递进名称“ testit . txt ”和' w '字符(写入文件)。

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'w' Open file, or create new file, for writing; discard existing contents, if any.

打开文件，创建新文件；将原有的内容去掉。

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Recipients can file Form W-4V to have a flat 10% withheld.

WSJ: Tax Tips for Life's Big Changes

Should employees file a new Form W-4 to adjust tax withholding?

FORBES: Fiscal Cliff, Dairy Cliff, What about the Payroll Tax Cliff?