Values of this type represent real numbers, with the usual limitations of IEEE-754 floating point type: it cannot represent very large or very small numbers, and the precision is limited to only about 15 digits. For complete details on the IEEE-754 standard and its limitations, see the Wikipedia article.
A floating-point constant may be preceded by a
+” or “
-” sign, followed by a string of one or
more digits containing a decimal point (“
For very large or small numbers, you may express the
number in exponential notation by appending a letter
e” followed by a power of
ten (which may be preceded by a sign).
For example, Avogadro's Number gives the number of atoms
of carbon in 12 grams of carbon12, and is written as
Python that would be “
Please note that calculations involving
float type are approximations. In calculator
mode, Python will display the numbers to their full
precision, so you may see a number that is very close to
what you expect, but not exact.
>>> 1.0/7.0 0.14285714285714285 >>> -2*-4.2e37 8.4000000000000004e+37