Vega strike Python Modules doc  0.5.1
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Data Structures | Functions | Variables
fpformat Namespace Reference

Data Structures

class  NotANumber
 

Functions

def extract
 
def unexpo
 
def roundfrac
 
def fix
 
def sci
 
def test
 

Variables

list __all__ = ["fix","sci","NotANumber"]
 
tuple decoder = re.compile(r'^([-+]?)0*(\d*)((?:\.\d*)?)(([eE][-+]?\d+)?)$')
 
string NotANumber = 'fpformat.NotANumber'
 

Detailed Description

General floating point formatting functions.

Functions:
fix(x, digits_behind)
sci(x, digits_behind)

Each takes a number or a string and a number of digits as arguments.

Parameters:
x:             number to be formatted; or a string resembling a number
digits_behind: number of digits behind the decimal point

Function Documentation

def fpformat.extract (   s) 
Return (sign, intpart, fraction, expo) or raise an exception:
sign is '+' or '-'
intpart is 0 or more digits beginning with a nonzero
fraction is 0 or more digits
expo is an integer

Definition at line 32 of file fpformat.py.

32 
33 def extract(s):
34  """Return (sign, intpart, fraction, expo) or raise an exception:
35  sign is '+' or '-'
36  intpart is 0 or more digits beginning with a nonzero
37  fraction is 0 or more digits
38  expo is an integer"""
39  res = decoder.match(s)
40  if res is None: raise NotANumber, s
41  sign, intpart, fraction, exppart = res.group(1,2,3,4)
42  if sign == '+': sign = ''
43  if fraction: fraction = fraction[1:]
44  if exppart: expo = int(exppart[1:])
45  else: expo = 0
46  return sign, intpart, fraction, expo
def fpformat.fix (   x,
  digs 
) 
Format x as [-]ddd.ddd with 'digs' digits after the point
and at least one digit before.
If digs <= 0, the point is suppressed.

Definition at line 87 of file fpformat.py.

References extract(), roundfrac(), and unexpo().

87 
88 def fix(x, digs):
89  """Format x as [-]ddd.ddd with 'digs' digits after the point
90  and at least one digit before.
91  If digs <= 0, the point is suppressed."""
92  if type(x) != type(''): x = `x`
93  try:
94  sign, intpart, fraction, expo = extract(x)
95  except NotANumber:
96  return x
97  intpart, fraction = unexpo(intpart, fraction, expo)
98  intpart, fraction = roundfrac(intpart, fraction, digs)
99  while intpart and intpart[0] == '0': intpart = intpart[1:]
100  if intpart == '': intpart = '0'
101  if digs > 0: return sign + intpart + '.' + fraction
102  else: return sign + intpart
def fpformat.roundfrac (   intpart,
  fraction,
  digs 
) 
Round or extend the fraction to size digs.

Definition at line 61 of file fpformat.py.

61 
62 def roundfrac(intpart, fraction, digs):
63  """Round or extend the fraction to size digs."""
64  f = len(fraction)
65  if f <= digs:
66  return intpart, fraction + '0'*(digs-f)
67  i = len(intpart)
68  if i+digs < 0:
69  return '0'*-digs, ''
70  total = intpart + fraction
71  nextdigit = total[i+digs]
72  if nextdigit >= '5': # Hard case: increment last digit, may have carry!
73  n = i + digs - 1
74  while n >= 0:
75  if total[n] != '9': break
76  n = n-1
77  else:
78  total = '0' + total
79  i = i+1
80  n = 0
81  total = total[:n] + chr(ord(total[n]) + 1) + '0'*(len(total)-n-1)
82  intpart, fraction = total[:i], total[i:]
83  if digs >= 0:
84  return intpart, fraction[:digs]
85  else:
86  return intpart[:digs] + '0'*-digs, ''
def fpformat.sci (   x,
  digs 
) 
Format x as [-]d.dddE[+-]ddd with 'digs' digits after the point
and exactly one digit before.
If digs is <= 0, one digit is kept and the point is suppressed.

Definition at line 103 of file fpformat.py.

References extract(), sre_parse.max, and roundfrac().

103 
104 def sci(x, digs):
105  """Format x as [-]d.dddE[+-]ddd with 'digs' digits after the point
106  and exactly one digit before.
107  If digs is <= 0, one digit is kept and the point is suppressed."""
108  if type(x) != type(''): x = `x`
109  sign, intpart, fraction, expo = extract(x)
110  if not intpart:
111  while fraction and fraction[0] == '0':
112  fraction = fraction[1:]
113  expo = expo - 1
114  if fraction:
115  intpart, fraction = fraction[0], fraction[1:]
116  expo = expo - 1
117  else:
118  intpart = '0'
119  else:
120  expo = expo + len(intpart) - 1
121  intpart, fraction = intpart[0], intpart[1:] + fraction
122  digs = max(0, digs)
123  intpart, fraction = roundfrac(intpart, fraction, digs)
124  if len(intpart) > 1:
125  intpart, fraction, expo = \
126  intpart[0], intpart[1:] + fraction[:-1], \
127  expo + len(intpart) - 1
128  s = sign + intpart
129  if digs > 0: s = s + '.' + fraction
130  e = `abs(expo)`
131  e = '0'*(3-len(e)) + e
132  if expo < 0: e = '-' + e
133  else: e = '+' + e
134  return s + 'e' + e
def fpformat.test ( ) 
Interactive test run.

Definition at line 135 of file fpformat.py.

References fix(), fileinput.input(), and sci().

135 
136 def test():
137  """Interactive test run."""
138  try:
139  while 1:
140  x, digs = input('Enter (x, digs): ')
141  print x, fix(x, digs), sci(x, digs)
142  except (EOFError, KeyboardInterrupt):
143  pass
def fpformat.unexpo (   intpart,
  fraction,
  expo 
) 
Remove the exponent by changing intpart and fraction.

Definition at line 47 of file fpformat.py.

47 
48 def unexpo(intpart, fraction, expo):
49  """Remove the exponent by changing intpart and fraction."""
50  if expo > 0: # Move the point left
51  f = len(fraction)
52  intpart, fraction = intpart + fraction[:expo], fraction[expo:]
53  if expo > f:
54  intpart = intpart + '0'*(expo-f)
55  elif expo < 0: # Move the point right
56  i = len(intpart)
57  intpart, fraction = intpart[:expo], intpart[expo:] + fraction
58  if expo < -i:
59  fraction = '0'*(-expo-i) + fraction
60  return intpart, fraction

Variable Documentation

list __all__ = ["fix","sci","NotANumber"]

Definition at line 16 of file fpformat.py.

tuple decoder = re.compile(r'^([-+]?)0*(\d*)((?:\.\d*)?)(([eE][-+]?\d+)?)$')

Definition at line 19 of file fpformat.py.

string NotANumber = 'fpformat.NotANumber'

Definition at line 30 of file fpformat.py.