Python：创建坐标列表（将字符串转换为int）

Question

I want to import several coordinates (could add up to 20.000) from an text file. These coordinates need to be added into a list, looking like the follwing:

coords = [[0,0],[1,0],[2,0],[0,1],[1,1],[2,1],[0,2],[1,2],[2,2]]

However when i want to import the coordinates i got the follwing error:

invalid literal for int() with base 10

I can't figure out how to import the coordinates correctly. Does anyone has any suggestions why this does not work? I think there's some problem with creating the integers. I use the following script:

Bronbestand = open("D:\\Documents\\SkyDrive\\afstuderen\\99 EEM - Abaqus 6.11.2\\scripting\\testuitlezen4.txt", "r")
headerLine = Bronbestand.readline()
valueList = headerLine.split(",")

xValueIndex = valueList.index("x")
#xValueIndex = int(xValueIndex)
yValueIndex = valueList.index("y")
#yValueIndex = int(yValueIndex)

coordList = []

for line in Bronbestand.readlines():
    segmentedLine = line.split(",")
    coordList.extend([segmentedLine[xValueIndex], segmentedLine[yValueIndex]])

coordList = [x.strip(' ') for x in coordList]
coordList = [x.strip('\n') for x in coordList]

coordList2 = []
#CoordList3 = [map(int, x) for x in coordList]

for i in coordList:
    coordList2 = [coordList[int(i)], coordList[int(i)]]

print "coordList = ", coordList
print "coordList2 = ", coordList2
#print "coordList3 = ", coordList3

The coordinates needed to be imported are looking like (this is "Bronbestand" in the script):

id,x,y,
      1,  -1.24344945,   4.84291601
      2,  -2.40876842,   4.38153362
      3,  -3.42273545,    3.6448431
      4,  -4.22163963,   2.67913389
      5,   -4.7552824,   1.54508495
      6,  -4.99013376, -0.313952595
      7,   -4.7552824,  -1.54508495
      8,  -4.22163963,  -2.67913389
      9,  -3.42273545,   -3.6448431

Thus the script should result in:

[[-1.24344945, 4.84291601],[-2.40876842, 4.38153362],[-3.42273545, 3.6448431],[-4.22163963, 2.67913389],[-4.7552824, 1.54508495],[-4.99013376,-0.313952595],[-4.7552824, -1.54508495],[-4.22163963, -2.67913389],[-3.42273545, -3.6448431]]

I also tried importing the coordinates with the native python csv parser but this didn't work either.

Thank you all in advance for the help!

Answer 1

Your numbers are not integers so the conversion to int fails.

Try using float(i) instead of int(i) to convert into floating point numbers instead.

>>> int('1.5')

Traceback (most recent call last):
  File "<pyshell#1>", line 1, in <module>
    int('1.5')
ValueError: invalid literal for int() with base 10: '1.5'
>>> float('1.5')
1.5

Answer 2

Other answers have said why your script fails, however, there is another issue here - you are massively reinventing the wheel.

This whole thing can be done in a couple of lines using the csv module and a list comprehension :

import csv

with open("test.csv") as file:
    data = csv.reader(file)
    next(data)
    print([[float(x) for x in line[1:]] for line in data])

Gives us:

[[-1.24344945, 4.84291601], [-2.40876842, 4.38153362], [-3.42273545, 3.6448431], [-4.22163963, 2.67913389], [-4.7552824, 1.54508495], [-4.99013376, -0.313952595], [-4.7552824, -1.54508495], [-4.22163963, -2.67913389], [-3.42273545, -3.6448431]]

We open the file, make a csv.reader() to parse the csv file, skip the header row, then make a list of the numbers parsed as floats, ignoring the first column.

As pointed out in the comments, as you are dealing with a lot of data, you may wish to iterate over the data lazily. While making a list is good to test the output, in general, you probably want a generator rather than a list. Eg:

([float(x) for x in line[1:]] for line in data)

Note that the file will need to remain open while you utilize this generator (remain inside the with block).