Python - Converting string values of list into float values

Question

I want to store the float values of list. The values are extracted from csv file.

The code I have written:

import numpy as np

import csv
from sklearn import datasets, metrics
from sklearn.model_selection import train_test_split
from neupy import algorithms, environment

environment.reproducible()

data1 = open('data.csv','r').read().split("\n")

target1 = open('target.csv','r').read().split("\n")

x1 = [[float(n) for n in e] for e in data1 ]
y1 = [[float(s) for s in f] for f in target1 ]
x_train, x_test, y_train, y_test = train_test_split(x1,y1,train_size=0.7)

pnn = algorithms.PNN(std=10,verbose=False)

pnn.train(x_train, y_train)
y_predicted = pnn.predict(x_test)
print(metrics.accuracy_score(y_test, y_predicted))

The error I am encountered with is:

WARNING (theano.configdefaults): g++ not detected ! Theano will be 
unable to execute optimized C-implementations (for both CPU and GPU) 
and will default to Python implementations. Performance will be 
severely degraded. To remove this warning, set Theano flags cxx to
an empty string.

Traceback (most recent call last):
  File "C:\Users\pc\AppData\Local\Programs\Python\Python36-32\pnn-3.py", line 16, in <module>
    x1 = [[float(n) for n in e] for e in data1 ]
  File "C:\Users\pc\AppData\Local\Programs\Python\Python36-32\pnn-3.py", line 16, in <listcomp>
    x1 = [[float(n) for n in e] for e in data1 ]
  File "C:\Users\pc\AppData\Local\Programs\Python\Python36-32\pnn-3.py", line 16, in <listcomp>
    x1 = [[float(n) for n in e] for e in data1 ]
ValueError: could not convert string to float: '.'

Welcome to StackOverflow. Please read How do I ask a good question? and How to create a Minimal, Complete, and Verifiable example, then come back and rephrase your question — Ohad Eytan
– Ohad Eytan, Commented Apr 23, 2017 at 15:02
I would say that e is already a string representing a float, so the conversion (kind of) works until it chokes on the dot. Try x1 = [float(n) for n in data1] — Jean-François Fabre
– Jean-François Fabre ♦, Commented Apr 23, 2017 at 15:06

Jean-François Fabre · Accepted Answer · 2017-04-23 15:08:05Z

3

when you do this:

data1 = open('data.csv','r').read().split("\n")

data1 is a list of strings

So then you do this:

x1 = [[float(n) for n in e] for e in data1 ]

you're iterating on strings, and then on the characters of the string. So conversion (kind of) works for the first digits of the first float, then chokes on . (ex: "3.1416": 3 is converted to a float (works, in a funny way), but then you encounter . and it fortunately fails).

You just forgot to split your line according to the csv separator.

I would use the csv module to split the lines into rows for me and do:

with open('data.csv','r') as f:
   cr = csv.reader(f,delimiter=";")  # change to whatever your delimiter is
   x1 = [[float(n) for n in row] for row in cr]

answered Apr 23, 2017 at 15:08

Jean-François Fabre♦

141k24 gold badges179 silver badges246 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Python - Converting string values of list into float values

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related