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Python Reference Manual |  |
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Python Reference Manual | |
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The binary arithmetic operations have the conventional priority levels. Note that some of these operations also apply to certain non-numeric types. Apart from the power operator, there are only two levels, one for multiplicative operators and one for additive operators:
The * (multiplication) operator yields the product of its
arguments. The arguments must either both be numbers, or one argument
must be an integer (plain or long) and the other must be a sequence.
In the former case, the numbers are converted to a common type and
then multiplied together. In the latter case, sequence repetition is
performed; a negative repetition factor yields an empty sequence.
The / (division) operator yields the quotient of its
arguments. The numeric arguments are first converted to a common
type. Plain or long integer division yields an integer of the same
type; the result is that of mathematical division with the `floor'
function applied to the result. Division by zero raises the
ZeroDivisionError exception.
The % (modulo) operator yields the remainder from the
division of the first argument by the second. The numeric arguments
are first converted to a common type. A zero right argument raises
the ZeroDivisionError exception. The arguments may be floating
point numbers, e.g., 3.14%0.7 equals 0.34 (since
3.14 equals 4*0.7 + 0.34.) The modulo operator always
yields a result with the same sign as its second operand (or zero);
the absolute value of the result is strictly smaller than the second
operand.
The integer division and modulo operators are connected by the
following identity: x == (x/y)*y + (x%y). Integer division and
modulo are also connected with the built-in function divmod():
divmod(x, y) == (x/y, x%y). These identities don't hold for
floating point and complex numbers; there similar identities hold
approximately where x/y is replaced by floor(x/y)) or
floor(x/y) - 1 (for floats),5.2 or floor((x/y).real) (for
complex).
The + (addition) operator yields the sum of its arguments.
The arguments must either both be numbers or both sequences of the
same type. In the former case, the numbers are converted to a common
type and then added together. In the latter case, the sequences are
concatenated.
The - (subtraction) operator yields the difference of its
arguments. The numeric arguments are first converted to a common
type.
floor(x/y) to be one larger than
(x-x%y)/y due to rounding. In such cases, Python returns
the latter result, in order to preserve that divmod(x,y)[0]
* y + x % y be very close to x.
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Python Reference Manual | |
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