How to outdent a block with emacs?

I can use C-x TAB for indenting 1 column, or C-u N C-x TAB for N columns.

How can I `outdent' a开发者_如何学Python block with emacs?

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You do the same, since C-x tab understands negative arguments.

So to outdent 3 columns:

C-u - 3 C-x TAB

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In python mode, for a marked region you also use C-c-< to outdent and C-c-> to indent

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Use rectangular operations. C-x r k - to kill a rectangle.

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Just like you mention for indenting:

C-u N C-x TAB

Just use a negative N:

C-u -N C-x TAB