read_csv doesn't read the column names correctly on this file?

Add parameter sep="\s+" or delim_whitespace=True to read_csv:

import pandas as pd

temp=u"""0 5
1 10
2 15
3 20
4 25"""
#after testing replace io.StringIO(temp) to filename
column_names = ['x','y']
df = pd.read_csv(pd.compat.StringIO(temp), sep="\s+", header = None, names = column_names)

print (df)
   x   y
0  0   5
1  1  10
2  2  15
3  3  20
4  4  25

Or:

column_names = ['x','y']
df = pd.read_csv(pd.compat.StringIO(temp),
                 delim_whitespace=True, 
                 header = None, 
                 names = column_names)

print (df)
   x   y
0  0   5
1  1  10
2  2  15
3  3  20
4  4  25

You could try this :

import pandas as pd    

column_names = ['x','y']
df = pd.read_csv('csv-file.csv',header=None)
df.columns = column_names