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| author | Mark Dickinson <dickinsm@gmail.com> | 2009-10-08 20:02:25 (GMT) |
|---|---|---|
| committer | Mark Dickinson <dickinsm@gmail.com> | 2009-10-08 20:02:25 (GMT) |
| commit | d5a713ec307766dc186913b238fbe3e92ad5fd73 (patch) | |
| tree | 9b77d9823bc962a7cb536241fdf22cf4385e903e /Doc/library/string.rst | |
| parent | 539bff4234d6e3c3183884625434b10b02f6cb05 (diff) | |
| download | cpython-d5a713ec307766dc186913b238fbe3e92ad5fd73.zip cpython-d5a713ec307766dc186913b238fbe3e92ad5fd73.tar.gz cpython-d5a713ec307766dc186913b238fbe3e92ad5fd73.tar.bz2 | |
Issue #7051: Clarify behaviour of 'g' and 'G'-style formatting.
Diffstat (limited to 'Doc/library/string.rst')
| -rw-r--r-- | Doc/library/string.rst | 32 |
1 files changed, 25 insertions, 7 deletions
diff --git a/Doc/library/string.rst b/Doc/library/string.rst index f5a1a3e..d01ddf1 100644 --- a/Doc/library/string.rst +++ b/Doc/library/string.rst @@ -446,15 +446,33 @@ The available presentation types for floating point and decimal values are: +---------+----------------------------------------------------------+ | ``'F'`` | Fixed point. Same as ``'f'``. | +---------+----------------------------------------------------------+ - | ``'g'`` | General format. This prints the number as a fixed-point | - | | number, unless the number is too large, in which case | - | | it switches to ``'e'`` exponent notation. Infinity and | - | | NaN values are formatted as ``inf``, ``-inf`` and | - | | ``nan``, respectively. | + | ``'g'`` | General format. For a given precision ``p >= 1``, | + | | this rounds the number to ``p`` significant digits and | + | | then formats the result in either fixed-point format | + | | or in scientific notation, depending on its magnitude. | + | | | + | | The precise rules are as follows: suppose that the | + | | result formatted with presentation type ``'e'`` and | + | | precision ``p-1`` would have exponent ``exp``. Then | + | | if ``-4 <= exp < p``, the number is formatted | + | | with presentation type ``'f'`` and precision | + | | ``p-1-exp``. Otherwise, the number is formatted | + | | with presentation type ``'e'`` and precision ``p-1``. | + | | In both cases insignificant trailing zeros are removed | + | | from the significand, and the decimal point is also | + | | removed if there are no remaining digits following it. | + | | | + | | Postive and negative infinity, positive and negative | + | | zero, and nans, are formatted as ``inf``, ``-inf``, | + | | ``0``, ``-0`` and ``nan`` respectively, regardless of | + | | the precision. | + | | | + | | A precision of ``0`` is treated as equivalent to a | + | | precision of ``1``. | +---------+----------------------------------------------------------+ | ``'G'`` | General format. Same as ``'g'`` except switches to | - | | ``'E'`` if the number gets to large. The representations | - | | of infinity and NaN are uppercased, too. | + | | ``'E'`` if the number gets too large. The | + | | representations of infinity and NaN are uppercased, too. | +---------+----------------------------------------------------------+ | ``'n'`` | Number. This is the same as ``'g'``, except that it uses | | | the current locale setting to insert the appropriate | |