President Obama had threatened to veto his own defense budget if the Congress added $1.75 billion to produce more F-22 Raptor aircraft.

VOA: standard.2009.07.21

You can also assign to a list, or to an element of a list. So ivy sub 1, f -15 or example, could be assigned minus 15, and that will actually mutate the list.

此外你还可以给一个数组，或者数组内部的元素赋值,比如ivy。sub，可以被赋值为，这确实改变了数组。

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