How to get list of the range consisting of floats? Why the below code is not working?
lons = list (range(80.0,90.0,0.05)) print (lons) 
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7 Answers
You can utilise a combination of takewhile and count (from 2.7 onwards), if you didn't want to write your own function, eg:
from itertools import takewhile, count my_range = list(takewhile(lambda L: L < 90, count(80, 0.05))) 
3 Comments
IceArdor
obviously you'll want to check that min_val <= max_val, otherwise
takewhile will run infinitely.
Jonathon Reinhart
Your function suffers from the same round-off errors as this one. Even the docs suggest against using floating-point values in
count.
Jon Clements
@JonathonReinhart indeed... put anything that gives a sensible result when
+'d.... such as a decimal.Decimal - the question was how to get a range of floats - this provides that... whether the result is ultimately desirable is another thing :)You can use a generator function:
from math import ceil def solve(start, end, step): #http://stackoverflow.com/a/10986098/846892 for i in xrange(int(ceil((end-start)/step))): yield start + step*i print list(solve(80.0, 90.0, 0.5)) #[80.0, 80.5, 81.0, 81.5, 82.0, 82.5, 83.0, 83.5, 84.0, 84.5, 85.0, 85.5, 86.0, 86.5, 87.0, 87.5, 88.0, 88.5, 89.0, 89.5] Or using NumPy:
>>> import numpy as np >>> np.arange(80., 90., .5) array([ 80. , 80.5, 81. , 81.5, 82. , 82.5, 83. , 83.5, 84. , 84.5, 85. , 85.5, 86. , 86.5, 87. , 87.5, 88. , 88.5, 89. , 89.5]) 
1 Comment
Jonathon Reinhart
Your function suffers from the same round-off errors as this one.
From the Python docs for range:
The arguments must be plain integers.
1 Comment
Tim
This is true, but it doesn't help the questioner get a range of floats.
range just takes intergers. You can form a range and multiply them by floats to get the numbers you require, like this
lons = [80+x*0.05 for x in range(0,200)] Be aware you might end up with small rounding "errors" for that many numbers.
2 Comments
Jonathon Reinhart
You're not accumulating the floating-point values, so you shouldn't have any round-off error, right?
doctorlove
@JonathonReinhart I got roundoffs on 2.6 but not 2.7
range only works for integers. See the documentation at http://docs.python.org/2/library/functions.html#range
The functionality you're looking for is:
def floatrange(min_val, max_val, step): val=min_val while val < max_val: yield val val += step 
Comments
You can create your own range function to manage floats.
def n_range(x, y, jump):
... while x < y:
... yield x
... x += jump
...
lons = list (n_range(80.0,90.0,0.05))print (lons)
Comments
Someone I respect once said:
There's no point in floating point.
So the actual answer to your question is: You're doing it wrong :)
But as that wouldn't exactly count as an answer here on SO, here's a frange function that could work for you. It elevates everything to ints and yields the floats you want.
As you probably can tell by the code, decpl stands for "decimal places" and defines the resolution of the floating point argument. I don't think there's an easy way to reliably derive that from the value passed to the step argument. (Comments are welcome)
def frange(start, stop, step, decpl): exp = 10.0 ** decpl for i in xrange(int(start * exp), int(stop*exp), int(step*exp)): yield i / exp print list(frange(80, 90, 0.1, 1)) 