Is there a one step operation to select all the records in a QGIS layer?

In current versions of QGIS, you can find the Select All Features tool in the toolbar:

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Original answer:

Select all is available in SelectPlus menu. You might have to activate this plugin but it should be shipped with 1.7.0.

Good question! I've not found a single button, but you can do the attribute table invert method without having to select one record first. At least with version 1.7.0.

I'm sure @underdark will come up with some alternative; but if not, it would be worth putting in a feature request.

If you want to do it from the Python QGIS API or create a dedicated button for this, you just need to reuse the selectAll() method from class QgsVectorLayer (don't know when it appeared).

Considering a vector layer selected in your layer tree, you can try iface.activeLayer().selectAll()