How to Read Data from Text File Into Pandas?   

The following step-by-step example shows how to load data from a text file into Pandas. We can use:

• read_csv() function
  • it handles various delimiters, including commas, tabs, and spaces
• pd.read_fwf()
  • read fixed-width formatted lines into DataFrame

Let's cover both cases into examples:

read_csv - delimited file

To read a text into Pandas DataFrame we can use method read_csv() and provide the separator:

import pandas as pd
df = pd.read_csv('data.txt', sep=',')

Where sep argument specifies the separator. Separator can be continuous - '\s+'.

Other useful parameters are:

• header=None - does the file contain headers
• names=["a", "b", "c"] - the column names
• skiprows=[0,1] - skip rows
• index_col=True - use index from the file

read_fwf - fixed-width file

To read data from a fixed-width file in Pandas we can use read_fwf. Suppose we have a file 'data.txt' like:

John   35	123 A
Jane D 28	45  E
Bob	42	678 D

We can see that columns are aligned by position rather than separated by delimiters. Since the columns are separated by fixed widths:

• first column - 7 chars
  • (0, 7)
• second - 2 chars
  • (7, 9)

we can't use read_csv() with a separator. Instead we will:

• specify the column widths
• read the fixed-width file into a DataFrame

import pandas as pd

colspecs = [(0, 7), (7, 9), (13, 17), (17, 18)]

df = pd.read_fwf('data.txt', colspecs=colspecs, header=None, names=['name', 'age', 'score', 'class'])
df

The result is:

Pandas read text file line by line

To read a text file line by line into a pandas DataFrame we can:

• create an empty DataFrame
• create an iterator to read the file line by line
• iterate over the iterator and append each line to the DataFrame
• reset the index of the DataFrame

import pandas as pd

df = pd.DataFrame()

iterator = pd.read_csv('data.txt', header=None, iterator=True, chunksize=1)

for chunk in iterator:
	df = df.append(chunk)

df = df.reset_index(drop=True)

Pandas read text file with pattern

As an alternative we can use list comprehension to read files and filter it.

Let's work with the following file:

John   35	123 A
Pattern
Jane D 28	45  E
Bob	42	678 D
End of pattern

We can find the numbers of the start and end lines by matching pattern:

a=[]
with open('data.txt',"r") as r:
	a=r.readlines()
a=[x.replace("\n","") for x in a]
start = a.index("Pattern") +1
end = a.index("End of pattern")
start, end

After that we can read the file with read_fwf or read_csv and filter the lines:

import pandas as pd

df = pd.read_fwf('data.txt', colspecs=colspecs, header=None, names=['name', 'age', 'score', 'class'])

df = df[start:end]

Which give us:

Summary

We've seen three different ways of reading and loading text file into Pandas DataFrame. We covered how to read delimited or fixed-length files with Pandas.

We also saw how to read text files line by line and how to filter csv or text file by pattern.