1"""General floating point formatting functions.
2
3Functions:
4fix(x, digits_behind)
5sci(x, digits_behind)
6
7Each takes a number or a string and a number of digits as arguments.
8
9Parameters:
10x:             number to be formatted; or a string resembling a number
11digits_behind: number of digits behind the decimal point
12"""
13from warnings import warnpy3k
14warnpy3k("the fpformat module has been removed in Python 3.0", stacklevel=2)
15del warnpy3k
16
17import re
18
19__all__ = ["fix","sci","NotANumber"]
20
21# Compiled regular expression to "decode" a number
22decoder = re.compile(r'^([-+]?)(\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')
28
29try:
30    class NotANumber(ValueError):
31        pass
32except TypeError:
33    NotANumber = 'fpformat.NotANumber'
34
35def 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    intpart = intpart.lstrip('0');
45    if sign == '+': sign = ''
46    if fraction: fraction = fraction[1:]
47    if exppart: expo = int(exppart[1:])
48    else: expo = 0
49    return sign, intpart, fraction, expo
50
51def unexpo(intpart, fraction, expo):
52    """Remove the exponent by changing intpart and fraction."""
53    if expo > 0: # Move the point left
54        f = len(fraction)
55        intpart, fraction = intpart + fraction[:expo], fraction[expo:]
56        if expo > f:
57            intpart = intpart + '0'*(expo-f)
58    elif expo < 0: # Move the point right
59        i = len(intpart)
60        intpart, fraction = intpart[:expo], intpart[expo:] + fraction
61        if expo < -i:
62            fraction = '0'*(-expo-i) + fraction
63    return intpart, fraction
64
65def roundfrac(intpart, fraction, digs):
66    """Round or extend the fraction to size digs."""
67    f = len(fraction)
68    if f <= digs:
69        return intpart, fraction + '0'*(digs-f)
70    i = len(intpart)
71    if i+digs < 0:
72        return '0'*-digs, ''
73    total = intpart + fraction
74    nextdigit = total[i+digs]
75    if nextdigit >= '5': # Hard case: increment last digit, may have carry!
76        n = i + digs - 1
77        while n >= 0:
78            if total[n] != '9': break
79            n = n-1
80        else:
81            total = '0' + total
82            i = i+1
83            n = 0
84        total = total[:n] + chr(ord(total[n]) + 1) + '0'*(len(total)-n-1)
85        intpart, fraction = total[:i], total[i:]
86    if digs >= 0:
87        return intpart, fraction[:digs]
88    else:
89        return intpart[:digs] + '0'*-digs, ''
90
91def fix(x, digs):
92    """Format x as [-]ddd.ddd with 'digs' digits after the point
93    and at least one digit before.
94    If digs <= 0, the point is suppressed."""
95    if type(x) != type(''): x = repr(x)
96    try:
97        sign, intpart, fraction, expo = extract(x)
98    except NotANumber:
99        return x
100    intpart, fraction = unexpo(intpart, fraction, expo)
101    intpart, fraction = roundfrac(intpart, fraction, digs)
102    while intpart and intpart[0] == '0': intpart = intpart[1:]
103    if intpart == '': intpart = '0'
104    if digs > 0: return sign + intpart + '.' + fraction
105    else: return sign + intpart
106
107def sci(x, digs):
108    """Format x as [-]d.dddE[+-]ddd with 'digs' digits after the point
109    and exactly one digit before.
110    If digs is <= 0, one digit is kept and the point is suppressed."""
111    if type(x) != type(''): x = repr(x)
112    sign, intpart, fraction, expo = extract(x)
113    if not intpart:
114        while fraction and fraction[0] == '0':
115            fraction = fraction[1:]
116            expo = expo - 1
117        if fraction:
118            intpart, fraction = fraction[0], fraction[1:]
119            expo = expo - 1
120        else:
121            intpart = '0'
122    else:
123        expo = expo + len(intpart) - 1
124        intpart, fraction = intpart[0], intpart[1:] + fraction
125    digs = max(0, digs)
126    intpart, fraction = roundfrac(intpart, fraction, digs)
127    if len(intpart) > 1:
128        intpart, fraction, expo = \
129            intpart[0], intpart[1:] + fraction[:-1], \
130            expo + len(intpart) - 1
131    s = sign + intpart
132    if digs > 0: s = s + '.' + fraction
133    e = repr(abs(expo))
134    e = '0'*(3-len(e)) + e
135    if expo < 0: e = '-' + e
136    else: e = '+' + e
137    return s + 'e' + e
138
139def test():
140    """Interactive test run."""
141    try:
142        while 1:
143            x, digs = input('Enter (x, digs): ')
144            print x, fix(x, digs), sci(x, digs)
145    except (EOFError, KeyboardInterrupt):
146        pass
147