python3 ValueError: could not convert string to float , value = float(value) is not valid

Question

I have a problem with a command of python. I want my program to read a specific line from my file, and here I haven't problem. The problem is when I have to convert the line in a float (I need of float to calculate some equation). My program is:

f=open('coeff.txt')
lines=f.readlines()

k1=lines[0]

k1 = float(k1)


k2=lines[1]

k2 = float(k2)


k3=lines[2]

k3 = float(k3)

k4=lines[3]

k4 = float(k4)

And the file coeff.txt is:

1.2*1e-1   

6.00*1e-34

1.13*1e-4

6.9*1e-16

that is 1.2*10^(-1) , 6*10^(-34), 1.13*10^(-4), 6.9*10^(-16)

and I get the error:

ValueError: could not convert string to float: '6.00*1e-34\n'

(obviously that this error is referred to each line.

Can you help me, please?

Answer 1

Python doesn't know how to interpret '6.00*1e-34\n' as a float. You will have to clean your data before you can actually use it.

Eventually, you will want to have each line in a format like this: 6.00e-34

Looking at it closely, it seems like the only differences are the \n at the end of the line, and the 1* in the middle.

You can get rid of the newline character at the end of the string (\n) by calling the .strip() method, and replace *1 with an empty string to get to the above format.

val = '6.00*1e-34\n'
cleaned_val = val.strip().replace('*1', '')
print(float(cleaned_val))
>>> 6e-34

Edit: It seems like the presence of the newline character doesn't really matter - so you only need to replace the *1 part of your string. I'm leaving it in anyway.

Answer 2

Your problem is the operator *