Creates inclusive regular sequences or fully closed ranges which differs from the half-open ranges of Python. Also accepts floating point arguments.
| Python |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 | def seq(*args, **kwargs):
"""
seq(n1, n2, base=, by=, length=, ztol=)
Minimum number is 1 and maximum number of args is 2.
Any misspecification will result in an empty list.
Current version has no extensive error checking!
"""
# Undefined key?
unknownKeys = [key for key in kwargs.keys() if key not in ["base","length","by","ztol"]]
if unknownKeys:
return []
# Tolerance for floating point computations.
if kwargs.has_key("ztol"):
ztol = kwargs["ztol"]
else:
ztol = 1.0e-14
# Normally, base is 0 since Python indexing is 0-based.
if kwargs.has_key("base"):
base = kwargs["base"]
else:
base = 0
nargs, nkwargs = len(args), len(kwargs)
if nargs == 1:
n1 = float(args[0])
if kwargs.has_key("length"):
L = kwargs["length"]
if kwargs.has_key("by"):
d = kwargs["by"]
else:
d = 1.0
return [n1 + i * d for i in range(L)]
elif kwargs.has_key("by"):
d = kwargs["by"]
if abs(d) < ztol: # too small by.
return []
if (n1 > base and d > 0) or (n1 < base and d < 0):
return [] # wrong sign for value of by
L = int((float(base-n1) / float(d)) + 1 + ztol)
return [n1 + i * d for i in range(L) ]
else:
L = int((abs(n1 - base)) + 1 + ztol)
if n1 > base:
return [base + i for i in range(L) ]
else:
return [base - i for i in range(L) ]
elif nargs == 2:
n1 = args[0]
n2 = args[1]
nparms = 0
if kwargs.has_key("by") and kwargs.has_key("length"):
return [] # Too many parameters
if kwargs.has_key("by"):
d = kwargs["by"]
if n2 > n1 and d < 0:
return [] # Wrong sign for by value.
L = int((float(n2 - n1) / d) + 1 + ztol)
elif kwargs.has_key("length"):
L = kwargs["length"]
if L <= 0:
return []
d = float((n2 - n1)) / float(L)
else:
if n2 < n1:
d = -1
elif n2 > n1:
d = 1
else:
d = 0
L = int(abs(n2 - n1) + 1 + ztol)
return [n1 + i*d for i in range(L) ]
return []
if __name__ == "__main__":
print "seq(2)", seq(2)
print "seq(2, base=1)", seq(2, base=1)
print "seq(2.6)", seq(2.6)
print "seq(2.6, length=4)", seq(2.6, length=4)
print "seq(2.6, length=4, by=0.1)", seq(2.6, length=4, by=0.1)
print "seq(2.6, length=4, by=-0.1)", seq(2.6, length=4, by=-0.1)
print "seq(2.6, length=4, by= 0)", seq(2.6, length=4, by=0)
print "seq(2, by=0.1)", seq(2.6, by= 0.1)
print "seq(2.6, by=-0.1)", seq(2.6, by=-0.1)
print "seq(2.6, by=-0.1, base = 1)", seq(2.6, by=-0.1, base=1)
print "seq(-2)", seq(-2)
print "seq(-2, base=1)", seq(-2, base=1)
print "seq(-2.6)", seq(-2.6)
print "seq(-2.6, by=0.1, base = 1)", seq(-2.6, by=0.1, base=1)
print "seq(-2.6, by=-0.1)", seq(-2.6, by=-0.1)
print "seq(2.6, by= 0)", seq(2.6, by=0)
print "seq(-2.6, 5)", seq(-2.6, 5)
print "seq(5, -2.6)", seq(5, -2.6)
print "seq(-2.6, 5.1, by=0.1)", seq(-2.6, 5.1, by=0.1)
print "seq(-2.6, 5, by=-0.1)", seq(-2.6, 5, by=-0.1)
print "seq(-2.6, 5, by=-0.1, length=10)",seq(-2.6, 5, by=-0.1, length=10)
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Discussion
The seq() function returns a regular inclusive sequence as a list. It differs from a Python range in that the sequence includes all end-points. User can optionally specify the length, step and base (if only one non-keyword argument is given).
Run the test example to see the effects of key arguments. The function is somewhat similar to the seq() function in R. The behavior is not he same as the arange() function of scipy (or Numeric).
See also frange() function in ASPN Cookbook Python Recipe #66472
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