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I wrote the following function:

def read_coordinates(filename):
    invoerfile = open(filename)
    lines = invoerfile.readlines()
    for line in lines:
        seperate_coordinate_rows = line.split("=")
        for seperate_coordinate_row in seperate_coordinate_rows:
            row = seperate_coordinate_row.split()
            print row

which gives me these lists:

['5,4', '4,5', '8,7']
['6,3', '3,2', '9,6', '4,3']
['7,6']
['9,8']
['5,5', '7,8', '6,5', '6,4']

What do I need to add to this function to get lists with floats as output?

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  • Can you post an example of the input? Commented Nov 28, 2013 at 13:20
  • If you post a sample of your input, someone here can possible come up with a better solution than this. Commented Nov 28, 2013 at 13:25
  • Instead of ['7,6'], it should be [7.6]. Is this what you want? Or should it be [7,6]? Commented Nov 28, 2013 at 13:30
  • Iw want 7.6, the answer I accepted was exactly what is was looking for Commented Nov 28, 2013 at 13:34

5 Answers 5

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4

You can use this:

row = map(lambda x: float(x.replace(',','.')), row)

The above will return a generator in Python 3.x, which may or may not suit your needs. If you need an actual list, you have two options:

# Convert the generator to a list (bad option)
row = list(row)

# Or use a list comprehension
row = [float(x.replace(',','.')) for x in row]
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3 Comments

This will return a generator in Python 3.x
Why not use a list comprehension here? [float(x.replace(',', '.')) for x in row]. It'll be faster than the map (no stack push), and work the same in both Python 2 and 3.
Fixed it, although I don't think the OP is using Python 3.x, nor will he care about the really tiny performance improvement of using listcomp vs maps.
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Put this inside your inner for loop.

row = [float(x.replace(',', '.') for x in row]
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To make sure you get a list it's best to use a list comprehension, since map doesn't return a list in Python3

row = [float(x.replace(",", ".")) for x in seperate_coordinate_row.split()]
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0

replace the last two lines with

row = [float(item.replace(',', '.')) for item in seperate_coordinate_row.split()]
print row
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0

Map your values to float():

row = map(float, seperate_coordinate_row.replace(',', '.').split())

map() calls the first argument for each value in the second value, effectively returning a list of float values.

The .replace() here is needed to turn your format to one that float() recognizes.

Demo:

>>> line = '5,4 4,5 8,7'
>>> map(float, line.replace(',', '.').split())
[5.4, 4.5, 8.7]

If you are using Python 3, or just want to use a list comprehension anyway, use:

[float(item.replace(',', '.') for item in seperate_coordinate_row.split()]

Here the .replace() is applied to each split item instead.

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2 Comments

You'd first need to replace "," with ".".
Shouldnt we use locales to process this data?

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