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Old 10-01-2010, 08:46 AM   #1
marozsas
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python: how to avoid spaces ?


Hi,

in the code below:
Code:
x= "123.45"
for i in range (1, 10):
  print "%s;" % x,
print
The output is:
Code:
123.45; 123.45; 123.45; 123.45; 123.45; 123.45; 123.45; 123.45; 123.45;
Looks like the "," operator in the print inside the loop is adding a space for its own.
I want to print the sequence WITHOUT spaces. Something like this:
Code:
123.45;123.45;123.45;123.45;123.45;123.45;123.45;123.45;123.45;
but I couldn't figure out how to do this.....

How to print a sequence, inside a loop, without that space ?
 
Old 10-01-2010, 09:07 AM   #2
ghostdog74
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you don't need the for loop

Code:
>>> x="123.45"
>>> ((x +",")*10)[:-1]
'123.45,123.45,123.45,123.45,123.45,123.45,123.45,123.45,123.45,123.45'
or list comprehension
Code:
>>> ','.join([ x for i in range(10) ])
'123.45,123.45,123.45,123.45,123.45,123.45,123.45,123.45,123.45,123.45'
 
Old 10-01-2010, 09:28 AM   #3
marozsas
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hi ghostdog74 !
the loop in the example, is, well, an example.
in fact I am iterating over rows returned from a sql query and the output is CSV formated.

The problem here is how to use print with the no newline inside the loop to build a row of data. (at the end of the loop I print a newline to just start another loop for the next row.
The extra spaces are unwanted because some colunms are strings (and must be exact strings, without extra spaces) and other columns are float numbers which the extra space cause the data to be interpreted as a text, not as a number, when it is loaded in another system.

Last edited by marozsas; 10-01-2010 at 09:30 AM.
 
Old 10-01-2010, 09:29 AM   #4
GrapefruiTgirl
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I don't program in python so forgive me if this is a less than divine way of doing this:
Code:
#!/usr/bin/python

import sys

x= "123.45"
for i in range (1, 10):
  sys.stdout.write (x); print ";",
print
I got the hint from here: http://bytes.com/topic/python/answer...t-ending-comma
 
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Old 10-01-2010, 09:48 AM   #5
Sergei Steshenko
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Quote:
Originally Posted by ghostdog74 View Post
you don't need the for loop

Code:
>>> x="123.45"
>>> ((x +",")*10)[:-1]
'123.45,123.45,123.45,123.45,123.45,123.45,123.45,123.45,123.45,123.45'
or list comprehension
Code:
>>> ','.join([ x for i in range(10) ])
'123.45,123.45,123.45,123.45,123.45,123.45,123.45,123.45,123.45,123.45'
OMG !!! What do I see in Python ?! There is more than way to do it !
 
Old 10-01-2010, 09:56 AM   #6
marozsas
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Hi Celine, thanks, your solution works but it is kind of awkward isn't ? At this point, it is more a matter of doing the thing in proper way in first place than solving the problem itself.

In fact, what I already did is:
Code:
myprogram.py | sed -e 's/; /;/g' > output.csv
 
Old 10-01-2010, 10:07 AM   #7
GrapefruiTgirl
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Hi!

Is my idea awkward? I really don't know - that's the first python code I have ever put together.

But, I question whether your solution in post #6 is 'less awkward' or 'the proper way'; I would think that the 'proper way' would not involve an external tool to remove the space - rather, the space wouldn't be present to begin with. Therefore, I prefer my way over post #6.

I suspect Sergei or Ghostdog or any number of other members have a better grasp that you or I evidently do, so maybe they will tell us what's the "best" way. I figure Ghostdog's second suggestion could be adapted to your original query also.

Cheers!
 
Old 10-01-2010, 10:11 AM   #8
ghostdog74
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Quote:
Originally Posted by marozsas View Post
hi ghostdog74 !
the loop in the example, is, well, an example.
in fact I am iterating over rows returned from a sql query and the output is CSV formated.
show examples, and show desired output!
 
Old 10-01-2010, 10:18 AM   #9
marozsas
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Quote:
Originally Posted by GrapefruiTgirl View Post
Hi!

But, I question whether your solution in post #6 is 'less awkward' or 'the proper way'; I would think that the 'proper way' would not involve an external tool to remove the space - rather, the space wouldn't be present to begin with. Therefore, I prefer my way over post #6.

Cheers!
Hey, don't get me wrong !

my the code in #6 is not a solution! It is not even a patch ! It is just how I manage to delivery the info other people need and have more time to solve the problem exclusively using python.

So, I still have the problem. I still don't known how to print inside a loop, without newlines and extras spaces.

Of course, like Sergei told, there is more than a way to do this and yours is so good as any other:
Code:
x= "123.45"
output= ""
for i in range (1,10):
  output= output + x + ';'
print output
but the original problem remains: Using the "," operator with print, how to avoid the extra spaces....

Anyway, sorry by the "awkward" - it was not a good word after all....but it is not what I was looking for in first place.

Last edited by marozsas; 10-01-2010 at 12:55 PM.
 
Old 10-01-2010, 10:19 AM   #10
ghostdog74
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Quote:
Originally Posted by Sergei Steshenko View Post
OMG !!! What do I see in Python ?! There is more than way to do it !
You are hopelessly misguided. These are not different ways to use a syntax. Not like Perl. So many for loop syntax, so many open() syntax. etc
 
Old 10-01-2010, 10:20 AM   #11
GrapefruiTgirl
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No problem

"awkward" may yet turn out to be the right word! I'm interested in seeing what turns up though, if there's an exact solution to what you ask (and I'm sure there is).
 
Old 10-01-2010, 10:22 AM   #12
ghostdog74
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Quote:
Originally Posted by GrapefruiTgirl View Post
x= "123.45"
for i in range (1, 10):
sys.stdout.write (x); print ";",
print
[/code]
you will end up with a ";" at the end.
 
Old 10-01-2010, 10:23 AM   #13
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Quote:
Originally Posted by ghostdog74 View Post
you will end up with a ";" at the end.
Yes, thanks! That part I did figure out.
 
Old 10-01-2010, 10:26 AM   #14
ghostdog74
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Quote:
Originally Posted by marozsas View Post
but the original problem remains: Using the "," operator with print, how to avoid the extra spaces....
Python's print statement is "designed" that way, for simple visualization of your output. The "pythonic" way to do what you want is using str.join() like my second example. And I have been using it as well to print sql statement output so yes, do consider using that method. (there certainly is no need to call extra sed or tools)

that said, if you have Python 2.6+ (or Python 3+)
Code:
>>> from __future__ import print_function # for Python 2.6 
>>> print( *[x for i in range(10)], sep=',')
123.45,123.45,123.45,123.45,123.45,123.45,123.45,123.45,123.45,123.45

Last edited by ghostdog74; 10-01-2010 at 10:47 AM.
 
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Old 10-01-2010, 12:44 PM   #15
marozsas
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Quote:
Originally Posted by ghostdog74 View Post
Python's print statement is "designed" that way, for simple visualization of your output.
Ok. I understand that. Makes sense to me. Thanks for the enlightenment.

So I will use others ways not related to "print x," to achieve my goals, since "print x," will, "by design", print an extra space anyway.

I can't use the way you suggested because "x" is not a constant. Just to clarify:

Code:
import kinterbasdb as k

# create a connection to database
con = k.connect(dsn='host:database', user='USER', password='PASSWD')

# Create a Cursor object that operates in the context of Connection con:
cur = con.cursor()

# SQL statement
SQL="select f1, f2, f3, ..fn from table where several conditions;"

# execute the SQL query
cur.execute(SQL)

# interate over the records
out= "row title"
for (f1, f2, f3,...fn) in cur:
   a= functionA (f1, f2, f3, ...fn)
   b= functionB (f1, f2, f3, ...fn)
   x= functionC (a, b)
   out= out + ';' + x
print out
(you see now why I reduced the problem in the first place ? If I am using a database, or how the "x" is evaluated it is not important - just "print x," printing a extra space is the problem.)

Anyway, it was fun, as always.
 
  


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