ValueError: 无法将字符串转换为浮点数：'-'

Question

#turns the text file into a list with each coordinates on a seperate line.
with open('AV.txt', 'r') as file:
    file_data = file.read()
file_data = file_data.replace('],', ']\n')
with open('AV.txt', 'w') as file:
    file.write(file_data)

#puts the vertices into an array
array = []
with open('AV.txt') as f:
    for line in f:
        array.append(line.strip("\n"))

#individual vertices according to their axis
x_array = [i[1] for i in array]
y_array = [i[7] for i in array]
z_array = [i[13] for i in array]

#Finds the maximum, minimum, and median for the x vertices
max_x = -1000000000000
min_x = 1000000000000
x_array_sorted = sorted(x_array)
length_x_array = len(x_array_sorted)
half_point_x = length_x_array//2
median_x = x_array_sorted[half_point_x]

n = 0
for q in x_array:
    if float(x_array[n]) > float(max_x):
        max_x = x_array[n]
    if float(x_array[n]) < float(min_x):
        min_x = x_array[n]
    n = n + 1

When I run this code I get this value error

ValueError: could not convert string to float: '-'.

when it gets to

if float(x_array[n]) > float(max_x):

I don't know how to get my code to accept that some of the coordinates are negative and therefore have a '-' in front of them. Any ideas? Thank you.

An example line of text in the file that is being opened and read: [27.36, -31.24, 26.03]

Answer 1

To solve the problem you have, you can just convert the list comprehensions into ints.

#individual vertices according to their axis
x_array = [int(i[1]) for i in array]
y_array = [int(i[7]) for i in array]
z_array = [int(i[13]) for i in array]

The above code is iterating through array 3 times to create the three list items. I recommend you to convert it into a single loop like this.

for i in array:
    x_array.append(int(i[1])
    y_array.append(int(i[7])
    z_array.append(int(i[13])

Also, can I recommend that you minimize the I/O by processing the values in memory.

For example: you can change the below code to fewer lines:

If file_data is the information you read from AV.txt , then the below 3 lines of code will get you the list you are looking for.

file_data = '[1, 2, 3, 4, 5][20, 59, 60, 80][30, 15, 16]'
file_data = file_data.replace(']',']\n')
arr = file_data.strip('\n')
print (arr)

The output for this will be:

[1, 2, 3, 4, 5]
[20, 59, 60, 80]
[30, 15, 16]

You can replace most of the below code with the above code.

#turns the text file into a list with each coordinates on a seperate line.
with open('AV.txt', 'r') as file:
    file_data = file.read()
file_data = file_data.replace('],', ']\n')
with open('AV.txt', 'w') as file:
    file.write(file_data)

#puts the vertices into an array
array = []
with open('AV.txt') as f:
    for line in f:
        array.append(line.strip("\n"))