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I am new to python. I want my script to print everything but the last line. I tried a [:-1] but I cant get it work. I know the code below isnt perfect as it is one of my first but it does everything I need it to do expect ... I dont want it to print the very last line of the string. Please help

import requests


html = requests.get("")

html_str = html.content
Html_file= open("fb_remodel.csv",'a')
html_str = html_str.replace('},', '},\n')
html_str = html_str.replace(':"', ',')
html_str = html_str.replace('"', '')
html_str = html_str.replace('T', ' ')
html_str = html_str.replace('+', ',')
html_str = html_str.replace('_', ',')
Html_file.write(html_str[:-1])
Html_file.close()
user2748540
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2 Answers2

4

html_str is a string, not a list.

You can do something like this:

txt='''\
Line 1
line 2
line 3
line 4
last line'''

print txt.rpartition('\n')[0]

Or

print txt.rsplit('\n',1)[0]

The different between rpartition and rsplit can been seen in the docs. I would choose between one or the other based on what I wanted to happen if the split character is not found in the target string.

BTW, You may want to write your file open this way:

with open("fb_remodel.csv",'a') as Html_file:
    # blah blah
    # at the end -- close is automatic.

The use of with is a very common Python idiom.

If you want a general method of dropping the last n lines, this will do it:

First create a test file:

# create a test file of 'Line X of Y' type
with open('/tmp/lines.txt', 'w') as fout:      
    start,stop=1,11
    for i in range(start,stop):
        fout.write('Line {} of {}\n'.format(i, stop-start))

Then you can use a deque are loop and do an action:

from collections import deque

with open('/tmp/lines.txt') as fin:
    trim=6                              # print all but the last X lines
    d=deque(maxlen=trim+1)
    for line in fin:
        d.append(line)
        if len(d)<trim+1: continue
        print d.popleft().strip()

Prints:

Line 1 of 10
Line 2 of 10
Line 3 of 10
Line 4 of 10

If you print the deque d, you can see where the lines went:

>>> d
deque(['Line 5 of 10\n', 'Line 6 of 10\n', 'Line 7 of 10\n', 'Line 8 of 10\n', 'Line 9 of 10\n', 'Line 10 of 10\n'], maxlen=7)
dawg
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    It may be worth pointing out that if your string comes from a Windows text file, this may leave a trailing `\r`. In this case, the string comes from a source literal, and in the OP's real case, it comes from `requests`, so in either case, I don't think that's an issue to worry about, so this answer is perfect. – abarnert Nov 12 '13 at 05:34
  • @abarnert: Yes, that is very true. Would opening the file in universal line mode fix that tho? Not being a Windoz guy -- I can only speculate. – dawg Nov 12 '13 at 05:42
  • Yeah, that would work too. The only problem would be if you had a text file that you didn't open in universal newlines mode (or a sequence of lines read from stdin, or something like that). – abarnert Nov 12 '13 at 05:49
-2

Use an array to populate all text one by one. Then use a while() or if condition. This may help you: Reading & Writing files in Python

Example:

>>> for line in f:
        print line

Then use a break before the last iteration occurs.

Muhammad Maqsoodur Rehman
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  • You can't put strings in an [`array`](http://docs.python.org/2/library/array.html). And I'm not sure how he'd use an `if` condition. And the `replace` will be a lot less efficient if he has to do it line by line. (Also, note that in some cases his `replace` calls even change the number of lines, which will be confusing.) – abarnert Nov 12 '13 at 05:32
  • In the edited version, "use a break before the last iteration occurs" isn't very helpful, because there's no way to _know_ the last iteration has occurred until it's already too late. – abarnert Nov 12 '13 at 05:33