Read file as a list of tuples

Question

I want to read a text file using Python. My list must be like this:

mylist = [(-34.968398, -6.487265), (-34.969448, -6.488250),
          (-34.967364, -6.492370), (-34.965735, -6.582322)]

My text file is:

-34.968398,-6.487265
-34.969448,-6.488250
-34.967364,-6.492370
-34.965735,-6.582322

My Python code:

f = open('t3.txt', 'r')
l = f.readlines()
print l

My results:

['-34.968398 -6.487265\n', '-34.969448 -6.488250\n', 
 '-34.967364 -6.492370\n', '-34.965735 -6.582322\n']

Answer 1

One of the most efficient way to read delimited data like this is using numpy.genfromtxt. For example

>>> import numpy as np
>>> np.genfromtxt(r't3.txt', delimiter=',')
array([[-34.968398,  -6.487265],
       [-34.969448,  -6.48825 ],
       [-34.967364,  -6.49237 ],
       [-34.965735,  -6.582322]])

Otherwise you could use a list comprehension to read line by line, split on ',', convert the values to float, and finally produce a list of tuple

with open('t3.txt') as f:
    mylist = [tuple(map(float, i.split(','))) for i in f]

Note that when you open a file using with it will take care of closing itself afterwards so you don't have to.

Answer 2

Yes Cyber solution is best.

For beginners

1. Read file in Read mode.
2. Iterate lines by readlines() or readline()
3. Use split(",") method to split line by '
4. Use float to convert string value to float. OR We can use eval() also.
5. Use list append() method to append tuple to list.
6. Use try except to prevent code from break.

Code:

p = "/home/vivek/Desktop/test.txt"
result = []
with open(p, "rb") as fp:
    for i in fp.readlines():
        tmp = i.split(",")
        try:
            result.append((float(tmp[0]), float(tmp[1])))
            #result.append((eval(tmp[0]), eval(tmp[1])))
        except:pass

print result

Output:

$ python test.py 
[(-34.968398, -6.487265), (-34.969448, -6.48825), (-34.967364, -6.49237), (-34.965735, -6.582322)]

Note: A readline() reads a single line from the file.

Answer 3

This code should do it:

ifile=open("data/t2mG_00", "r")
lines=ifile.readlines()
data=[tuple(line.strip().split()) for line in lines]
print(data[0])