Python: Capitalise specific words in a text file

user_8988742 0
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I am trying to write a python script to format SQL codes for better readability.

eg. converting specific lowercase words to uppercase: select -> SELECT

I am trying to do this using the reading and writing function in Python. However, I am stuck. Here is my code:

words = ['select', 'from', 'where']
w = open('03_TextUpper.txt', 'w')

with open('03_TextLower.txt', 'r') as file:

    for line in file:
        for word in line.split():
            if word in words:
                w.write( word.upper() )

    w.write( line )

This prints out the uppercase of the specific words, but does not remove the lowercase words.

Is there a better way of writing this in Python?

python-3.x text python
4 Answers

I suggest you do this is two stages:

words = ['select', 'from', 'where']

with open('03_TextUpper.txt') as f_input:
    text = f_input.read()

with open('03_TextUpper.txt', 'w') as f_output:
    for word in words:
        text = text.replace(word, word.upper())

    f_output.write(text)

First read the whole file into memory and make the necessary changes. Next open the file for writing and write it back.

It uses a Python string replace() to replace each word with its uppercase alternative. It does this for the whole file in one go without needing to split the file up.

This can be improved with the use of a regular expression to spot word boundaries:

import re

words = ['select', 'from', 'where']
uppercase = lambda x: x.group(1).upper()
re_replace = re.compile(r'\b({})\b'.format('|'.join(words)))

with open('03_TextUpper.txt') as f_input:
    text = f_input.read()

with open('03_TextUpper.txt', 'w') as f_output:
    f_output.write(re_replace.sub(uppercase, text))

The regular expression is able to carry out all of the replacements in a single call.

user_49857330

You're opening a read and write in the same instance. Try closing your read function and opening a new write function when it's done, and it could solve the problem.

user_77366480

You can iterate over the file once, and then write the generated list to the output file:

words = ['select', 'from', 'where']
data = [i.strip('\n').split() for i in open('03_TextLower.txt')]
new_words = [[b for b in i if b.lower() in words] for i in data]

with open('03_TextUpper.txt', 'w') as f:
   for line in new_words:
       for word in line:
          f.write("{}\n".format(word))
user_73267380

Third party library sqlparse will do this:

>>> sql = 'select * from foo where id in (select id from bar);'
>>> print sqlparse.format(sql, reindent=True, keyword_case='upper')
SELECT *
FROM foo
WHERE id IN
  (SELECT id
   FROM bar);
user_10844160
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