Lo que todo programador debería saber sobre aritmética de punto flotante
Formatting corrections
+7
-9
+7
-9
content/languages/python.html
+7
-9
content/languages/python.html
···
7
7
--------
8
8
Almost all platforms map Python floats to [IEEE 754](/formats/fp/)
9
9
double precision.
10
-
11
-
f = 0.1
10
+
f = 0.1
12
11
13
12
Decimal Types
14
13
-------------
15
14
Python has an [arbitrary-precision](/formats/exact/) decimal type named <code>Decimal</code> in the <code>decimal</code> module, which
16
15
also allows to choose the [rounding mode](/errors/rounding/).
17
-
a = Decimal('0.1')
18
-
b = Decimal('0.2')
19
-
c = a + b # returns a Decimal representing exactly 0.3
20
-
16
+
a = Decimal('0.1')
17
+
b = Decimal('0.2')
18
+
c = a + b # returns a Decimal representing exactly 0.3
21
19
22
20
How to Round
23
21
------------
24
22
To get a string:
25
-
"%.2f" % 1.2399 # returns "1.24"
23
+
"%.2f" % 1.2399 # returns "1.24"
26
24
"%.3f" % 1.2399 # returns "1.240"
27
25
"%.2f" % 1.2 # returns "1.20"
28
26
To print to standard output:
29
27
print "%.2f" % 1.2399 # just use print and string formatting
30
-
If you need a specific [rounding mode](/errors/rounding/) and other parameters can be defined in a Context object:
31
-
getcontext().prec = 7
28
+
Specific [rounding modes](/errors/rounding/) and other parameters can be defined in a Context object:
29
+
getcontext().prec = 7
32
30
33
31
Resources
34
32
---------