将文件作为元组列表读取

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])