I have a list which consists of float values but they're too detailed to proceed. I know we can shorten them by using the ["%.f" % variable] operator, like:
result = [359.70000000000005]
result = "%.2f" % result
result = [359.70]
My question is how can I turn a list of values into their rounded equivalents without using an iterator. I've tried something, but it throws a TypeError:
list = [0.30000000000000004, 0.5, 0.20000000000000001]
list = "%.2f" % list
TypeError: not all arguments converted during string formatting
How can I provide a clean list like:
list = [0.30, 0.5, 0.20]
gandreadis
2,8472 gold badges27 silver badges37 bronze badges
asked Mar 16, 2011 at 13:37
1
"%.2f" does not return a clean float. It returns a string representing this float with two decimals.
my_list = [0.30000000000000004, 0.5, 0.20000000000000001]
my_formatted_list = [ '%.2f' % elem for elem in my_list ]
returns:
['0.30', '0.50', '0.20']
Also, don't call your variable list. This is a reserved word for list creation. Use some other
name, for example my_list.
If you want to obtain [0.30, 0.5, 0.20] [or at least the floats that are the closest possible], you can try this:
my_rounded_list = [ round[elem, 2] for elem in my_list ]
returns:
[0.29999999999999999, 0.5, 0.20000000000000001]
gandreadis
2,8472 gold badges27 silver badges37 bronze badges
answered Mar 16, 2011 at 13:39
eumiroeumiro
198k33 gold badges294 silver badges259 bronze badges
4
If you really want an iterator-free solution, you can use numpy and its array round function.
import numpy as np
myList = list[np.around[np.array[myList],2]]
answered Mar 25, 2018 at 4:37
john ktejikjohn ktejik
5,6674 gold badges48 silver badges53 bronze badges
2
You
might want to look at Python's decimal module, which can make using floating point numbers and doing arithmetic with them a lot more intuitive. Here's a trivial example of one way of using it to "clean up" your list values:
>>> from decimal import *
>>> mylist = [0.30000000000000004, 0.5, 0.20000000000000001]
>>> getcontext[].prec = 2
>>> ["%.2f" % e for e in mylist]
['0.30', '0.50', '0.20']
>>> [Decimal["%.2f" % e] for e in mylist]
[Decimal['0.30'], Decimal['0.50'], Decimal['0.20']]
>>> data = [float[Decimal["%.2f" % e]] for e in mylist]
>>> data
[0.3, 0.5, 0.2]
answered Mar 16, 2011 at 14:08
martineaumartineau
115k25 gold badges160 silver badges282 bronze badges
0
mylist = [0.30000000000000004, 0.5, 0.20000000000000001]
myRoundedList = [round[x,2] for x in mylist]
# [0.3, 0.5, 0.2]
pzaenger
9,8513 gold badges39 silver badges44 bronze badges
answered Oct 21, 2018 at 17:42
Silvia42Silvia42
811 silver badge1 bronze badge
You can use the built-in
map along with a lambda expression:
my_list = [0.2111111111, 0.5, 0.3777777777]
my_list_rounded = list[map[lambda x: round[x, ndigits=2], my_list]]
my_list_rounded
Out[3]: [0.21, 0.5, 0.38]
Alternatively you could also create a named function for the rounding up to a specific digit using partial from the
functools module for working with higher order functions:
from functools import partial
my_list = [0.2111111111, 0.5, 0.3777777777]
round_2digits = partial[round, ndigits=2]
my_list_rounded = list[map[round_2digits, my_list]]
my_list_rounded
Out[6]: [0.21, 0.5, 0.38]
answered Sep 8, 2020 at 18:22
jojojojo
9,4182 gold badges48 silver badges69 bronze badges
Another option which doesn't require numpy is:
precision = 2
myRoundedList = [int[elem*[10**precision]+delta]/[10.0**precision] for elem in myList]
# delta=0 for floor
# delta = 0.5 for round
# delta = 1 for ceil
answered May 16, 2018 at 15:55
Easiest way :
import numpy as np
np.round[list,2]
answered Jul 4 at 14:42
1