Reading Files Backwards in Python

When we typically read a file, the contents are read line by line from the beginning. However, there are cases where we want to read the last line first. For example, if the data in a file is written with the latest record at the bottom, we want to read the latest record first. To meet this requirement, we can install the required package using the following command.

pip install file-read-backwards

But before reading the file backwards, let’s read the contents line by line so that we can compare the results after reading in reverse.

with open ("PathGodFather.txt", "r") as BigFile:
    data=BigFile.readlines()

# Print each line
    for i in range(len(data)):
    print "Line No- ",i
    print data[i]

When we run the above program, we get the following output:

Line No- 0
Vito Corleone is the aging don (head) of the Corleone Mafia Family.

Line No-1
His youngest son Michael has returned from WWII just in time to see the wedding of Connie Corleone (Michael's sister) to Carlo Rizzi.

Line No-2
All of Michael's family is involved with the Mafia, but Michael just wants to live a normal life. Drug dealer Virgil Sollozzo is looking for Mafia families to offer him protection in exchange for a profit of the drug money.

Line No-3
He approaches Don Corleone about it, but, much against the advice of the Don's lawyer Tom Hagen, the Don is morally against the use of drugs, and turns down the offer.

Line No-4
This does not please Sollozzo, who has the Don shot down by some of his hit men.

Line No-5
The Don barely survives, which leads his son Michael to begin a violent mob war against Sollozzo and tears the Corleone family apart.

Read lines backward

Now we use the installed module to read the file backwards.

from file_read_backwards import FileReadBackwards

with FileReadBackwards("PathGodFather.txt", encoding="utf-8") as BigFile:

# getting lines by lines starting from the last line up
    for line in BigFile:
        print line

When we run the above program, we get the following output –

The Don barely survives, which leads his son Michael to begin a violent mob war against Sollozzo and tears the Corleone family apart.
This does not please Sollozzo, who has the Don shot down by some of his hit men.
He approaches Don Corleone about it, but, much against the advice of the Don's lawyer Tom Hagen, the Don is morally against the use of drugs, and turns down the offer.
All of Michael's family is involved with the Mafia, but Michael just wants to live a normal life. Drug dealer Virgil Sollozzo is looking for Mafia families to offer him protection in exchange for profit from the drug money.
His youngest son, Michael, has returned from World War II just in time to see the wedding of Connie Corleone (Michael's sister) to Carlo Rizzi.
Vito Corleone is the aging don (head) of the Corleone Mafia Family.

You can verify that the order of the lines you read is reversed.

Reading Words in Reverse Order

We can also read the words in a file in reverse order. To do this, we first read the lines in reverse order and then tokenize the words using the reverse function. In the following example, we use the package and the nltk module to print the word tokens from the same file in reverse order.

import nltk
from file_read_backwards import FileReadBackwards

with FileReadBackwards("PathGodFather.txt", encoding="utf-8") as BigFile:

# getting lines by lines starting from the last line up
# And tokenizing with applying reverse()
    for line in BigFile:
        word_data= line
        nltk_tokens = nltk.word_tokenize(word_data)
        nltk_tokens.reverse()
        print(nltk_tokens)

When we run the above program, we get the following output −

['.', 'apart', 'family', 'Corleone', 'the', 'tears', 'and', 'Sollozzo', 'against', 'war', 'mob', 'violent', 'a', 'begin', 'to', 'Michael', 'son', 'his', 'leads', 'which', ',', 'srvives', 'barely', 'Don', 'The']
['.', 'men', 'hit', 'his', 'of', 'some', 'by', 'down', 'shot', 'Don', 'the', 'has', 'who', ',', 'Sollozzo', 'please', 'not', 'does', 'This']
['.', 'offer', 'the', 'down', 'trns', 'and', ',', 'drgs', 'of', 'se', 'the', 'against', 'morally', 'is', 'Don', 'the', ',', 'Hagen', 'Tom', 'lawyer', "'s", 'Don', 'the', 'of', 'advice', 'the', 'against', 'mch', ',', 'bt', ',', 'it', 'abot', 'Corleone', 'Don', 'approaches', 'He']
['.', 'money', 'drg', 'the', 'of', 'profit', 'a', 'for', 'exchange', 'in', 'protection', 'him', 'offer', 'to', 'families', 'Mafia', 'for', 'looking', 'is', 'Sollozzo', 'Virgil', 'dealer', 'Drg', '.', 'life', 'normal', 'a', 'live', 'to', 'wants', 'jst', 'Michael', 'bt', ',', 'Mafia', 'the', 'with', 'involved', 'is', 'family', "'s", 'Michael', 'of', 'All']
['.', 'Rizzi', 'Carlo', 'to', ')', 'sister', "'s", 'Michael', '(', 'Corleone', 'Connie', 'of', 'wedding', 'the', 'see', 'to', 'time', 'in', 'jst', 'WWII', 'from', 'retrned', 'has', 'Michael', 'son', 'yongest', 'His']
['.', 'Family', 'Mafia', 'Corleone', 'the', 'of', ')', 'head', '(', 'don', 'aging', 'the', 'is', 'Corleone', 'Vito']