Why is Python showing 'ValueError: could not convert string to float'?

问题

I have a CSV containing numbers which I am trying to convert to floats.

filename = "filename.csv"
enclosed_folder = "path/to/Folder"
full_path = os.path.join(enclosed_folder,filename)

with open(full_path) as input_data:
    temp = input_data.readlines()
    n = len(temp) #int(temp.pop(0))
    matrix = [x.split(" ") for x in temp]
    for i in range(n):
        for j in range(n):
            matrix[i][j] = float(matrix[i][j])
    input_data.close()

When I open the file in any text editor, it does not show the \n at the end of each row.

But running the python code shows the `ValueError: could not convert string to float' because of '\n' being present at the end of each row.

Traceback (most recent call last):
  File "hierarchical-clustering.py", line 37, in <module>
    matrix[i][j] = float(matrix[i][j])
ValueError: could not convert string to float: '1,0.058824,0.076923,0.066667,0.055556,0.058824,0.071429,0.052632,0.076923,0.0625,0.0625,0.055556,0.055556,0.05,0.066667,0,0,0.055556,0.0625,0.058824,0.058824,0.047619,0.055556,0.0625,0,0.052632,0.066667,0.055556,0.0625,0.058824,0.041667,0.066667,0.058824,0.071429,0.066667,0.076923,0,0.083333,0.052632,0.071429,0.076923,0,0.0625,0.076923,0.058824,0.076923,0.055556,0,0.0625,0.071429,0.0625,0.0625,0.083333,0,0,0,0.058824,0.0625,0,0.058824,0.0625,0.0625,0.066667,0.0625,0.052632,0.066667,0.076923,0.058824,0.071429,0.066667,0.058824,0.071429,0.058824,0.071429,0.058824,0.071429,0.071429\n'

So, how do I fix this error?

EDIT: I used strip() as well as rstrip() as suggested in some of the answers to remove whitespaces, but still the error does not go away:

Traceback (most recent call last):
  File "hierarchical-clustering.py", line 37, in <module>
    matrix[i][j] = float(matrix[i][j].rstrip())
ValueError: could not convert string to float: '1,0.058824,0.076923,0.066667,0.055556,0.058824,0.071429,0.052632,0.076923,0.0625,0.0625,0.055556,0.055556,0.05,0.066667,0,0,0.055556,0.0625,0.058824,0.058824,0.047619,0.055556,0.0625,0,0.052632,0.066667,0.055556,0.0625,0.058824,0.041667,0.066667,0.058824,0.071429,0.066667,0.076923,0,0.083333,0.052632,0.071429,0.076923,0,0.0625,0.076923,0.058824,0.076923,0.055556,0,0.0625,0.071429,0.0625,0.0625,0.083333,0,0,0,0.058824,0.0625,0,0.058824,0.0625,0.0625,0.066667,0.0625,0.052632,0.066667,0.076923,0.058824,0.071429,0.066667,0.058824,0.071429,0.058824,0.071429,0.058824,0.071429,0.071429'

回答1:

The error is due to your line parsing. You are separating on spaces, not commas, which is what should happen according to your screenshot. The key is looking at the error returned. It is trying to convert the entire line from a string into a float.

Change:

matrix = [x.split(" ") for x in temp]

To:

matrix = [x.split(",") for x in temp]

回答2:

you can use strip() to remove whitespaces from the string.

matrix[i][j] = float(matrix[i][j].strip())

If the commas are troubling you, you might want to .split(',') with commas and not spaces:

matrix = [x.strip().split(",") for x in temp]

回答3:

Remove the newline char with rstrip() like this:

matrix[i][j] = float(matrix[i][j].rstrip())

来源：https://stackoverflow.com/questions/44826250/why-is-python-showing-valueerror-could-not-convert-string-to-float