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| 55 | <H2><A NAME="SECTION007620000000000000000"></A><A NAME="decimal-decimal"></A> |
| 56 | <BR> |
| 57 | 5.6.2 Decimal objects |
| 58 | </H2> |
| 59 | |
| 60 | <P> |
| 61 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 62 | <td><nobr><b><span class="typelabel">class</span> <tt id='l2h-1195' xml:id='l2h-1195' class="class">Decimal</tt></b>(</nobr></td> |
| 63 | <td><var></var><big>[</big><var>value </var><big>[</big><var>, context</var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt> |
| 64 | <dd> |
| 65 | Constructs a new <tt class="class">Decimal</tt> object based from <var>value</var>. |
| 66 | |
| 67 | <P> |
| 68 | <var>value</var> can be an integer, string, tuple, or another <tt class="class">Decimal</tt> |
| 69 | object. If no <var>value</var> is given, returns <code>Decimal("0")</code>. If |
| 70 | <var>value</var> is a string, it should conform to the decimal numeric string |
| 71 | syntax: |
| 72 | |
| 73 | <P> |
| 74 | <div class="verbatim"><pre> |
| 75 | sign ::= '+' | '-' |
| 76 | digit ::= '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9' |
| 77 | indicator ::= 'e' | 'E' |
| 78 | digits ::= digit [digit]... |
| 79 | decimal-part ::= digits '.' [digits] | ['.'] digits |
| 80 | exponent-part ::= indicator [sign] digits |
| 81 | infinity ::= 'Infinity' | 'Inf' |
| 82 | nan ::= 'NaN' [digits] | 'sNaN' [digits] |
| 83 | numeric-value ::= decimal-part [exponent-part] | infinity |
| 84 | numeric-string ::= [sign] numeric-value | [sign] nan |
| 85 | </pre></div> |
| 86 | |
| 87 | <P> |
| 88 | If <var>value</var> is a <tt class="class">tuple</tt>, it should have three components, |
| 89 | a sign (<tt class="constant">0</tt> for positive or <tt class="constant">1</tt> for negative), |
| 90 | a <tt class="class">tuple</tt> of digits, and an integer exponent. For example, |
| 91 | "<tt class="samp">Decimal((0, (1, 4, 1, 4), -3))</tt>" returns <code>Decimal("1.414")</code>. |
| 92 | |
| 93 | <P> |
| 94 | The <var>context</var> precision does not affect how many digits are stored. |
| 95 | That is determined exclusively by the number of digits in <var>value</var>. For |
| 96 | example, "<tt class="samp">Decimal("3.00000")</tt>" records all five zeroes even if the |
| 97 | context precision is only three. |
| 98 | |
| 99 | <P> |
| 100 | The purpose of the <var>context</var> argument is determining what to do if |
| 101 | <var>value</var> is a malformed string. If the context traps |
| 102 | <tt class="constant">InvalidOperation</tt>, an exception is raised; otherwise, the |
| 103 | constructor returns a new Decimal with the value of <tt class="constant">NaN</tt>. |
| 104 | |
| 105 | <P> |
| 106 | Once constructed, <tt class="class">Decimal</tt> objects are immutable. |
| 107 | </dl> |
| 108 | |
| 109 | <P> |
| 110 | Decimal floating point objects share many properties with the other builtin |
| 111 | numeric types such as <tt class="class">float</tt> and <tt class="class">int</tt>. All of the usual |
| 112 | math operations and special methods apply. Likewise, decimal objects can |
| 113 | be copied, pickled, printed, used as dictionary keys, used as set elements, |
| 114 | compared, sorted, and coerced to another type (such as <tt class="class">float</tt> |
| 115 | or <tt class="class">long</tt>). |
| 116 | |
| 117 | <P> |
| 118 | In addition to the standard numeric properties, decimal floating point objects |
| 119 | also have a number of specialized methods: |
| 120 | |
| 121 | <P> |
| 122 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 123 | <td><nobr><b><tt id='l2h-1196' xml:id='l2h-1196' class="method">adjusted</tt></b>(</nobr></td> |
| 124 | <td><var></var>)</td></tr></table></dt> |
| 125 | <dd> |
| 126 | Return the adjusted exponent after shifting out the coefficient's rightmost |
| 127 | digits until only the lead digit remains: <code>Decimal("321e+5").adjusted()</code> |
| 128 | returns seven. Used for determining the position of the most significant |
| 129 | digit with respect to the decimal point. |
| 130 | </dl> |
| 131 | |
| 132 | <P> |
| 133 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 134 | <td><nobr><b><tt id='l2h-1197' xml:id='l2h-1197' class="method">as_tuple</tt></b>(</nobr></td> |
| 135 | <td><var></var>)</td></tr></table></dt> |
| 136 | <dd> |
| 137 | Returns a tuple representation of the number: |
| 138 | "<tt class="samp">(sign, digittuple, exponent)</tt>". |
| 139 | </dl> |
| 140 | |
| 141 | <P> |
| 142 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 143 | <td><nobr><b><tt id='l2h-1198' xml:id='l2h-1198' class="method">compare</tt></b>(</nobr></td> |
| 144 | <td><var>other</var><big>[</big><var>, context</var><big>]</big><var></var>)</td></tr></table></dt> |
| 145 | <dd> |
| 146 | Compares like <tt class="method">__cmp__()</tt> but returns a decimal instance: |
| 147 | <div class="verbatim"><pre> |
| 148 | a or b is a NaN ==> Decimal("NaN") |
| 149 | a < b ==> Decimal("-1") |
| 150 | a == b ==> Decimal("0") |
| 151 | a > b ==> Decimal("1") |
| 152 | </pre></div> |
| 153 | </dl> |
| 154 | |
| 155 | <P> |
| 156 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 157 | <td><nobr><b><tt id='l2h-1199' xml:id='l2h-1199' class="method">max</tt></b>(</nobr></td> |
| 158 | <td><var>other</var><big>[</big><var>, context</var><big>]</big><var></var>)</td></tr></table></dt> |
| 159 | <dd> |
| 160 | Like "<tt class="samp">max(self, other)</tt>" except that the context rounding rule |
| 161 | is applied before returning and that <tt class="constant">NaN</tt> values are |
| 162 | either signalled or ignored (depending on the context and whether |
| 163 | they are signaling or quiet). |
| 164 | </dl> |
| 165 | |
| 166 | <P> |
| 167 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 168 | <td><nobr><b><tt id='l2h-1200' xml:id='l2h-1200' class="method">min</tt></b>(</nobr></td> |
| 169 | <td><var>other</var><big>[</big><var>, context</var><big>]</big><var></var>)</td></tr></table></dt> |
| 170 | <dd> |
| 171 | Like "<tt class="samp">min(self, other)</tt>" except that the context rounding rule |
| 172 | is applied before returning and that <tt class="constant">NaN</tt> values are |
| 173 | either signalled or ignored (depending on the context and whether |
| 174 | they are signaling or quiet). |
| 175 | </dl> |
| 176 | |
| 177 | <P> |
| 178 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 179 | <td><nobr><b><tt id='l2h-1201' xml:id='l2h-1201' class="method">normalize</tt></b>(</nobr></td> |
| 180 | <td><var></var><big>[</big><var>context</var><big>]</big><var></var>)</td></tr></table></dt> |
| 181 | <dd> |
| 182 | Normalize the number by stripping the rightmost trailing zeroes and |
| 183 | converting any result equal to <tt class="constant">Decimal("0")</tt> to |
| 184 | <tt class="constant">Decimal("0e0")</tt>. Used for producing canonical values for members |
| 185 | of an equivalence class. For example, <code>Decimal("32.100")</code> and |
| 186 | <code>Decimal("0.321000e+2")</code> both normalize to the equivalent value |
| 187 | <code>Decimal("32.1")</code>. |
| 188 | </dl> |
| 189 | |
| 190 | <P> |
| 191 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 192 | <td><nobr><b><tt id='l2h-1202' xml:id='l2h-1202' class="method">quantize</tt></b>(</nobr></td> |
| 193 | <td><var>exp </var><big>[</big><var>, rounding</var><big>[</big><var>, context</var><big>[</big><var>, watchexp</var><big>]</big><var></var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt> |
| 194 | <dd> |
| 195 | Quantize makes the exponent the same as <var>exp</var>. Searches for a |
| 196 | rounding method in <var>rounding</var>, then in <var>context</var>, and then |
| 197 | in the current context. |
| 198 | |
| 199 | <P> |
| 200 | If <var>watchexp</var> is set (default), then an error is returned whenever |
| 201 | the resulting exponent is greater than <tt class="member">Emax</tt> or less than |
| 202 | <tt class="member">Etiny</tt>. |
| 203 | </dl> |
| 204 | |
| 205 | <P> |
| 206 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 207 | <td><nobr><b><tt id='l2h-1203' xml:id='l2h-1203' class="method">remainder_near</tt></b>(</nobr></td> |
| 208 | <td><var>other</var><big>[</big><var>, context</var><big>]</big><var></var>)</td></tr></table></dt> |
| 209 | <dd> |
| 210 | Computes the modulo as either a positive or negative value depending |
| 211 | on which is closest to zero. For instance, |
| 212 | "<tt class="samp">Decimal(10).remainder_near(6)</tt>" returns <code>Decimal("-2")</code> |
| 213 | which is closer to zero than <code>Decimal("4")</code>. |
| 214 | |
| 215 | <P> |
| 216 | If both are equally close, the one chosen will have the same sign |
| 217 | as <var>self</var>. |
| 218 | </dl> |
| 219 | |
| 220 | <P> |
| 221 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 222 | <td><nobr><b><tt id='l2h-1204' xml:id='l2h-1204' class="method">same_quantum</tt></b>(</nobr></td> |
| 223 | <td><var>other</var><big>[</big><var>, context</var><big>]</big><var></var>)</td></tr></table></dt> |
| 224 | <dd> |
| 225 | Test whether self and other have the same exponent or whether both |
| 226 | are <tt class="constant">NaN</tt>. |
| 227 | </dl> |
| 228 | |
| 229 | <P> |
| 230 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 231 | <td><nobr><b><tt id='l2h-1205' xml:id='l2h-1205' class="method">sqrt</tt></b>(</nobr></td> |
| 232 | <td><var></var><big>[</big><var>context</var><big>]</big><var></var>)</td></tr></table></dt> |
| 233 | <dd> |
| 234 | Return the square root to full precision. |
| 235 | </dl> |
| 236 | |
| 237 | <P> |
| 238 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 239 | <td><nobr><b><tt id='l2h-1206' xml:id='l2h-1206' class="method">to_eng_string</tt></b>(</nobr></td> |
| 240 | <td><var></var><big>[</big><var>context</var><big>]</big><var></var>)</td></tr></table></dt> |
| 241 | <dd> |
| 242 | Convert to an engineering-type string. |
| 243 | |
| 244 | <P> |
| 245 | Engineering notation has an exponent which is a multiple of 3, so there |
| 246 | are up to 3 digits left of the decimal place. For example, converts |
| 247 | <code>Decimal('123E+1')</code> to <code>Decimal("1.23E+3")</code> |
| 248 | </dl> |
| 249 | |
| 250 | <P> |
| 251 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 252 | <td><nobr><b><tt id='l2h-1207' xml:id='l2h-1207' class="method">to_integral</tt></b>(</nobr></td> |
| 253 | <td><var></var><big>[</big><var>rounding</var><big>[</big><var>, context</var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt> |
| 254 | <dd> |
| 255 | Rounds to the nearest integer without signaling <tt class="constant">Inexact</tt> |
| 256 | or <tt class="constant">Rounded</tt>. If given, applies <var>rounding</var>; otherwise, |
| 257 | uses the rounding method in either the supplied <var>context</var> or the |
| 258 | current context. |
| 259 | </dl> |
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