I need to read a .dat file in python which has 12 columns in total and millions of lines of rows. I need to divide column 2,3 and 4 with column 1 for my calculation. So before I load that .dat file, do I need to delete all the other unwanted columns? If not, how do I selectively declare the column and ask python to do the math?
an example of the .dat file would be data.dat
I am new to python , so a little instruction to open , read and calculation would be appreciated.
I have added the code I am using as a starter from your suggestion:
from sys import argv
import pandas as pd
script, filename = argv
txt = open(filename)
print "Here's your file %r:" % filename
print txt.read()
def your_func(row):
return row['x-momentum'] / row['mass']
columns_to_keep = ['mass', 'x-momentum']
dataframe = pd.read_csv('~/Pictures', delimiter="," , usecols=columns_to_keep)
dataframe['new_column'] = dataframe.apply(your_func, axis=1)
and also the error I get through it:
Traceback (most recent call last):
File "flash.py", line 18, in <module>
dataframe = pd.read_csv('~/Pictures', delimiter="," , usecols=columns_to_keep)
File "/home/trina/anaconda2/lib/python2.7/site-packages/pandas/io/parsers.py", line 529, in parser_f
return _read(filepath_or_buffer, kwds)
File "/home/trina/anaconda2/lib/python2.7/site-packages/pandas/io/parsers.py", line 295, in _read
parser = TextFileReader(filepath_or_buffer, **kwds)
File "/home/trina/anaconda2/lib/python2.7/site-packages/pandas/io/parsers.py", line 612, in __init__
self._make_engine(self.engine)
File "/home/trina/anaconda2/lib/python2.7/site-packages/pandas/io/parsers.py", line 747, in _make_engine
self._engine = CParserWrapper(self.f, **self.options)
File "/home/trina/anaconda2/lib/python2.7/site-packages/pandas/io/parsers.py", line 1119, in __init__
self._reader = _parser.TextReader(src, **kwds)
File "pandas/parser.pyx", line 518, in pandas.parser.TextReader.__cinit__ (pandas/parser.c:5030)
ValueError: No columns to parse from file
dat file to a CSV file in Python in four simple steps: (1) Install the Pandas library, (2) import the Pandas library, (3) read the CSV file as DataFrame, and (4) write the DataFrame to the file.
Most DAT files contain text, so you can open them with text editors, like Notepad, Notepad++, VS Code, and so on. If you are sure the information contained in the DAT file is a video or audio, then your media player can open it. If it's a PDF, then Adobe Reader can open it, and so on.
We can read data from a text file using read_table() in pandas. This function reads a general delimited file to a DataFrame object. This function is essentially the same as the read_csv() function but with the delimiter = '\t', instead of a comma by default.
To read a text file in Python, you follow these steps: First, open a text file for reading by using the open() function. Second, read text from the text file using the file read() , readline() , or readlines() method of the file object. Third, close the file using the file close() method.
After looking at your flash.dat
file, it's clear you need to do a little clean up before you process it. The following code converts it to a CSV file:
import csv
# read flash.dat to a list of lists
datContent = [i.strip().split() for i in open("./flash.dat").readlines()]
# write it as a new CSV file
with open("./flash.csv", "wb") as f:
writer = csv.writer(f)
writer.writerows(datContent)
Now, use Pandas to compute new column.
import pandas as pd
def your_func(row):
return row['x-momentum'] / row['mass']
columns_to_keep = ['#time', 'x-momentum', 'mass']
dataframe = pd.read_csv("./flash.csv", usecols=columns_to_keep)
dataframe['new_column'] = dataframe.apply(your_func, axis=1)
print dataframe
train=pd.read_csv("Path",sep=" ::",header=None)
Now you can access the dat file.
train.columns=["A","B","C"]# Number of columns you can see in the dat file.
then you can use this as csv files.
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With