Plotting pixel coordinates from CSV using Python

Question

From the image i have extracted the pixel co-ordinates ( x,y). To validate the co-ordinates , i am trying to plot those pixel co-ordinates. But i couldn't do it.

I tried to plot using turtle but still i am unable to do it

import turtle
import math

def drawMap():
    filename = r"build_coords.csv"

    trace = turtle.Turtle()
    trace.up()

    #scr = Screen()

    with open(filename, 'r') as f_input:
        for row in f_input:
            row = row.strip('()\n').split(',')
            x = float(row[0])
            y = float(row[1])
            trace.goto(x,y)
            trace.write(".")
    raw_input()
    #scr.mainloop()
drawMap()

ValueError: could not convert string to float: '0\t3'

Please kindly help to fix this. Thanks in advance

cdlane · Accepted Answer · 2017-07-21 06:30:25Z

1

Your input logic:

x, y = row.strip('()\n').split(',')

seems to imply input of the form:

(10, 20)
(30, 40)

which is not CSV. Your error message seems to imply input of the form:

10\t20
30\t40

So the key to answering your question correctly is for you to show us some sample input. Below is a rework of your code:

from turtle import Turtle, Screen

FILENAME = "build_coords.csv"

def drawMap(filename):
    trace = Turtle(visible=False)
    trace.penup()

    with open(filename) as f_input:
        header = f_input.readline().rstrip()  # "X,Y"

        for row in f_input:
            x, y = row.rstrip().split(',')  # 10,20\n
            trace.goto(float(x), float(y))
            trace.dot(2)

screen = Screen()

drawMap(FILENAME)

screen.exitonclick()

UPDATE

Based on your comments, I'm now assuming the data is CSV and looks like:

X,Y
0.0,3.0
0.0,4.0
0.0,5.0
0.0,6.0
0.0,8.0
0.0,10.0
0.0,11.0
0.0,15.0
0.0,16.0

I've updated the above code accordingly.

edited Jul 21, 2017 at 6:30

answered Jul 21, 2017 at 3:04

cdlane

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5 Comments

user6775896 Over a year ago

X,Y 0.0,3.0 0.0,4.0 0.0,5.0 0.0,6.0 0.0,8.0 0.0,10.0 0.0,11.0 0.0,15.0 0.0,16.0

user6775896 Over a year ago

X,Y 0.0,3.0 0.0,4.0 0.0,5.0 0.0,6.0 0.0,8.0 0.0,10.0 0.0,11.0 ### input above ###

user6775896 Over a year ago

ValueError: need more than 1 value to unpack , if i try to use the input above am getting error like this

cdlane Over a year ago

@vishal, I've updated my code to match the data in your comments -- I don't understand why your original code strips parentheses from the start and end of the data since there aren't any.

user6775896 Over a year ago

How to plot it faster ? Can i give Any other colour ? Please help me through it.

TukeV · Accepted Answer · 2017-07-20 12:56:28Z

0

Error message says that there is a tabulation ('\t'-character) inside your text, which is not removed in yor strip command. The '\t' character is still there when you try to convert a string to the floating point which causes the ValueError.

So, you could try find out why the input file has tabulations in the first place or strip those away too along with other whitespace characters.

answered Jul 20, 2017 at 12:56

TukeV

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