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| 53 | <H1><A NAME="SECTION0001100000000000000000"> |
| 54 | 10 PEP 331: Locale-Independent Float/String Conversions</A> |
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| 56 | |
| 57 | <P> |
| 58 | The <tt class="module">locale</tt> modules lets Python software select various |
| 59 | conversions and display conventions that are localized to a particular |
| 60 | country or language. However, the module was careful to not change |
| 61 | the numeric locale because various functions in Python's |
| 62 | implementation required that the numeric locale remain set to the |
| 63 | <code>'C'</code> locale. Often this was because the code was using the C library's |
| 64 | <tt class="cfunction">atof()</tt> function. |
| 65 | |
| 66 | <P> |
| 67 | Not setting the numeric locale caused trouble for extensions that used |
| 68 | third-party C libraries, however, because they wouldn't have the |
| 69 | correct locale set. The motivating example was GTK+, whose user |
| 70 | interface widgets weren't displaying numbers in the current locale. |
| 71 | |
| 72 | <P> |
| 73 | The solution described in the PEP is to add three new functions to the |
| 74 | Python API that perform ASCII-only conversions, ignoring the locale |
| 75 | setting: |
| 76 | |
| 77 | <P> |
| 78 | |
| 79 | <UL> |
| 80 | <LI><tt class="cfunction">PyOS_ascii_strtod(<var>str</var>, <var>ptr</var>)</tt> |
| 81 | and <tt class="cfunction">PyOS_ascii_atof(<var>str</var>, <var>ptr</var>)</tt> |
| 82 | both convert a string to a C <tt class="ctype">double</tt>. |
| 83 | </LI> |
| 84 | <LI><tt class="cfunction">PyOS_ascii_formatd(<var>buffer</var>, <var>buf_len</var>, <var>format</var>, <var>d</var>)</tt> converts a <tt class="ctype">double</tt> to an ASCII string. |
| 85 | </LI> |
| 86 | </UL> |
| 87 | |
| 88 | <P> |
| 89 | The code for these functions came from the GLib library |
| 90 | (<a class="url" href="http://developer.gnome.org/arch/gtk/glib.html">http://developer.gnome.org/arch/gtk/glib.html</a>), whose |
| 91 | developers kindly relicensed the relevant functions and donated them |
| 92 | to the Python Software Foundation. The <tt class="module">locale</tt> module |
| 93 | can now change the numeric locale, letting extensions such as GTK+ |
| 94 | produce the correct results. |
| 95 | |
| 96 | <P> |
| 97 | <div class="seealso"> |
| 98 | <p class="heading">See Also:</p> |
| 99 | |
| 100 | <dl compact="compact" class="seerfc"> |
| 101 | <dt><a href="http://www.python.org/peps/pep-0331.html" |
| 102 | title="Locale-Independent Float/String Conversions" |
| 103 | >PEP 331, <em>Locale-Independent Float/String Conversions</em></a> |
| 104 | <dd>Written by Christian R. Reis, and implemented by Gustavo Carneiro. |
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