How to format a list when I print it

Question

values = [[3.5689651969162908, 4.664618442892583, 3.338666695570425],
          [6.293153787450157, 1.1285723419142026, 10.923859694586376],
          [2.052506259736077, 3.5496423448584924, 9.995488620338277],
          [9.41858935127928, 10.034233496516803, 7.070345442417161]]

def flatten(values):

    new_values = []
    for i in range(len(values)):
        for v in range(len(values[0])):
            new_values.append(values[i][v])
    return new_values

v = flatten(values)
print("A 2D list contains:") 
print("{}".format(values))
print("The flattened version of the list is:")
print("{}".format(v))

I am flatting the 2D list to 1D, but I can format it. I know the (v) is a list, and I tried to use for loop to print it, but I still can't get the result I want. I am wondering are there any ways to format the list. I want to print the (v) as a result with two decimal places. Like this

[3.57, 4.66, 3.34, 6.29, 1.13, 10.92, 2.05, 3.55, 10.00, 9.42, 10.03, 7.07]

I am using the Eclipse and Python 3.0+.

IS this what you are looking for http://stackoverflow.com/questions/3264828/change-default-float-print-format — PyNEwbie, Jul 21 '16 at 14:08
If it is go ahead and delete your question so it does not get flagged for closure — PyNEwbie, Jul 21 '16 at 14:09
I tried to use for loop, like for i in v: print("{:.2f}".format(i)). but it doesn't work. it is printing a string rather than a list. — armchannelpatrick, Jul 21 '16 at 14:13

score 3 · Answer 1 · answered Jul 21 '16 at 14:15

3

You could use:

print(["{:.2f}".format(val) for val in v])

Note that you can flatten your list using itertools.chain:

import itertools
v = list(itertools.chain(*values))

answered Jul 21 '16 at 14:15

sirfz

4,097
23
37

score 0 · Answer 2 · edited May 23 '17 at 12:14

You can first flatten the list (as described here) and then use round to solve this:

flat_list = [number for sublist in l for number in sublist]
# All numbers are in the same list now
print(flat_list)
[3.5689651969162908, 4.664618442892583, 3.338666695570425, 6.293153787450157, ..., 7.070345442417161]

rounded_list = [round(number, 2) for number in flat_list]
# The numbers are rounded to two decimals (but still floats)
print(flat_list)
[3.57, 4.66, 3.34, 6.29, 1.13, 10.92, 2.05, 3.55, 10.00, 9.42, 10.03, 7.07]

This can be written shorter if we put the rounding directly into the list comprehension:

print([round(number, 2) for sublist in l for number in sublist])

score 0 · Answer 3 · answered Jul 21 '16 at 14:17

0

I would use the built-in function round(), and while I was about it I would simplify your for loops:

def flatten(values):
    new_values = []
    for i in values:
        for v in i:
            new_values.append(round(v, 2))
    return new_values

answered Jul 21 '16 at 14:17

cdarke

42,728
8
80
84

score 0 · Answer 4 · answered Jul 21 '16 at 14:19

0

How to flatten and transform the list in one line

[round(x,2) for b in [x for x in values] for x in b]

It returns a list of two decimals after the comma.

answered Jul 21 '16 at 14:19

HolyDanna

609
4
13

score 0 · Answer 5 · answered Jul 21 '16 at 14:22

0

One you have v you can use a list comprehension like:

formattedList = ["%.2f" % member for member in v]

output was as follows:

['3.57', '4.66', '3.34', '6.29', '1.13', '10.92', '2.05', '3.55', '10.00', '9.42', '10.03', '7.07']

Hope that helps!

answered Jul 21 '16 at 14:22

Marque Boseman

26
3

How to format a list when I print it

5 Answers5