issue5063: Fixes for building RPM on CentOS plus misc .spec file enhancements.
[python.git] / Lib / fpformat.py
blob71cbb25f3c8b9eb861415eca88358aeb049202ff
1 """General floating point formatting functions.
3 Functions:
4 fix(x, digits_behind)
5 sci(x, digits_behind)
7 Each takes a number or a string and a number of digits as arguments.
9 Parameters:
10 x: number to be formatted; or a string resembling a number
11 digits_behind: number of digits behind the decimal point
12 """
13 from warnings import warnpy3k
14 warnpy3k("the fpformat module has been removed in Python 3.0", stacklevel=2)
15 del warnpy3k
17 import re
19 __all__ = ["fix","sci","NotANumber"]
21 # Compiled regular expression to "decode" a number
22 decoder = re.compile(r'^([-+]?)0*(\d*)((?:\.\d*)?)(([eE][-+]?\d+)?)$')
23 # \0 the whole thing
24 # \1 leading sign or empty
25 # \2 digits left of decimal point
26 # \3 fraction (empty or begins with point)
27 # \4 exponent part (empty or begins with 'e' or 'E')
29 try:
30 class NotANumber(ValueError):
31 pass
32 except TypeError:
33 NotANumber = 'fpformat.NotANumber'
35 def extract(s):
36 """Return (sign, intpart, fraction, expo) or raise an exception:
37 sign is '+' or '-'
38 intpart is 0 or more digits beginning with a nonzero
39 fraction is 0 or more digits
40 expo is an integer"""
41 res = decoder.match(s)
42 if res is None: raise NotANumber, s
43 sign, intpart, fraction, exppart = res.group(1,2,3,4)
44 if sign == '+': sign = ''
45 if fraction: fraction = fraction[1:]
46 if exppart: expo = int(exppart[1:])
47 else: expo = 0
48 return sign, intpart, fraction, expo
50 def unexpo(intpart, fraction, expo):
51 """Remove the exponent by changing intpart and fraction."""
52 if expo > 0: # Move the point left
53 f = len(fraction)
54 intpart, fraction = intpart + fraction[:expo], fraction[expo:]
55 if expo > f:
56 intpart = intpart + '0'*(expo-f)
57 elif expo < 0: # Move the point right
58 i = len(intpart)
59 intpart, fraction = intpart[:expo], intpart[expo:] + fraction
60 if expo < -i:
61 fraction = '0'*(-expo-i) + fraction
62 return intpart, fraction
64 def roundfrac(intpart, fraction, digs):
65 """Round or extend the fraction to size digs."""
66 f = len(fraction)
67 if f <= digs:
68 return intpart, fraction + '0'*(digs-f)
69 i = len(intpart)
70 if i+digs < 0:
71 return '0'*-digs, ''
72 total = intpart + fraction
73 nextdigit = total[i+digs]
74 if nextdigit >= '5': # Hard case: increment last digit, may have carry!
75 n = i + digs - 1
76 while n >= 0:
77 if total[n] != '9': break
78 n = n-1
79 else:
80 total = '0' + total
81 i = i+1
82 n = 0
83 total = total[:n] + chr(ord(total[n]) + 1) + '0'*(len(total)-n-1)
84 intpart, fraction = total[:i], total[i:]
85 if digs >= 0:
86 return intpart, fraction[:digs]
87 else:
88 return intpart[:digs] + '0'*-digs, ''
90 def fix(x, digs):
91 """Format x as [-]ddd.ddd with 'digs' digits after the point
92 and at least one digit before.
93 If digs <= 0, the point is suppressed."""
94 if type(x) != type(''): x = repr(x)
95 try:
96 sign, intpart, fraction, expo = extract(x)
97 except NotANumber:
98 return x
99 intpart, fraction = unexpo(intpart, fraction, expo)
100 intpart, fraction = roundfrac(intpart, fraction, digs)
101 while intpart and intpart[0] == '0': intpart = intpart[1:]
102 if intpart == '': intpart = '0'
103 if digs > 0: return sign + intpart + '.' + fraction
104 else: return sign + intpart
106 def sci(x, digs):
107 """Format x as [-]d.dddE[+-]ddd with 'digs' digits after the point
108 and exactly one digit before.
109 If digs is <= 0, one digit is kept and the point is suppressed."""
110 if type(x) != type(''): x = repr(x)
111 sign, intpart, fraction, expo = extract(x)
112 if not intpart:
113 while fraction and fraction[0] == '0':
114 fraction = fraction[1:]
115 expo = expo - 1
116 if fraction:
117 intpart, fraction = fraction[0], fraction[1:]
118 expo = expo - 1
119 else:
120 intpart = '0'
121 else:
122 expo = expo + len(intpart) - 1
123 intpart, fraction = intpart[0], intpart[1:] + fraction
124 digs = max(0, digs)
125 intpart, fraction = roundfrac(intpart, fraction, digs)
126 if len(intpart) > 1:
127 intpart, fraction, expo = \
128 intpart[0], intpart[1:] + fraction[:-1], \
129 expo + len(intpart) - 1
130 s = sign + intpart
131 if digs > 0: s = s + '.' + fraction
132 e = repr(abs(expo))
133 e = '0'*(3-len(e)) + e
134 if expo < 0: e = '-' + e
135 else: e = '+' + e
136 return s + 'e' + e
138 def test():
139 """Interactive test run."""
140 try:
141 while 1:
142 x, digs = input('Enter (x, digs): ')
143 print x, fix(x, digs), sci(x, digs)
144 except (EOFError, KeyboardInterrupt):
145 pass