| 1 | """General floating point formatting functions.
|
|---|
| 2 |
|
|---|
| 3 | Functions:
|
|---|
| 4 | fix(x, digits_behind)
|
|---|
| 5 | sci(x, digits_behind)
|
|---|
| 6 |
|
|---|
| 7 | Each takes a number or a string and a number of digits as arguments.
|
|---|
| 8 |
|
|---|
| 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
|
|---|
| 16 |
|
|---|
| 17 | import re
|
|---|
| 18 |
|
|---|
| 19 | __all__ = ["fix","sci","NotANumber"]
|
|---|
| 20 |
|
|---|
| 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')
|
|---|
| 28 |
|
|---|
| 29 | try:
|
|---|
| 30 | class NotANumber(ValueError):
|
|---|
| 31 | pass
|
|---|
| 32 | except TypeError:
|
|---|
| 33 | NotANumber = 'fpformat.NotANumber'
|
|---|
| 34 |
|
|---|
| 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
|
|---|
| 49 |
|
|---|
| 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
|
|---|
| 63 |
|
|---|
| 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, ''
|
|---|
| 89 |
|
|---|
| 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
|
|---|
| 105 |
|
|---|
| 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
|
|---|
| 137 |
|
|---|
| 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
|
|---|
