remove all elements in a list with a particular value

[Lisa]

I am reading in data from a text file. I want to enter each value on
the line into a list and retain the order of the elements. The number
of elements and spacing between them varies, but a typical line looks
like:

' SRCPARAM 1 6.35e-07 15.00 340.00 1.10 3.0 '

Why does the following not work:

line = ' SRCPARAM 1 6.35e-07 15.00 340.00 1.10 3.0 '
li = line.split(' ')
for j,i in enumerate(li):
if i == '':
li.remove(i)

After the original split I get:
['', '', '', 'SRCPARAM', '', '', '1', '6.35e-07', '15.00', '',
'340.00', '', '', '1.10', '', '', '', '', '', '3.0', '', '', '']

And after the for loop I get:
['SRCPARAM', '1', '6.35e-07', '15.00', '340.00', '1.10', '', '', '',
'3.0', '', '', '']

It doesn't remove all of the empty elements. Is there a better way to
split the original string? Or a way to catch all of the empty
elements?

Thanks

[Larry Bates]

Lisa wrote:

I am reading in data from a text file. I want to enter each value on
the line into a list and retain the order of the elements. The number
of elements and spacing between them varies, but a typical line looks
like:

' SRCPARAM 1 6.35e-07 15.00 340.00 1.10 3.0 '

Why does the following not work:

line = ' SRCPARAM 1 6.35e-07 15.00 340.00 1.10 3.0 '
li = line.split(' ')
for j,i in enumerate(li):
if i == '':
li.remove(i)

After the original split I get:
['', '', '', 'SRCPARAM', '', '', '1', '6.35e-07', '15.00', '',
'340.00', '', '', '1.10', '', '', '', '', '', '3.0', '', '', '']

And after the for loop I get:
['SRCPARAM', '1', '6.35e-07', '15.00', '340.00', '1.10', '', '', '',
'3.0', '', '', '']

It doesn't remove all of the empty elements. Is there a better way to
split the original string? Or a way to catch all of the empty
elements?

Thanks

When you split on a space (' ') multiple spaces will return empty list
elements between them. Change to:

line = ' SRCPARAM 1 6.35e-07 15.00 340.00 1.10 3.0 '
li = line.split()

And you will get what you want:

['SRCPARAM', '1', '6.35e-07', '15.00', '340.00', '1.10', '3.0']

-Larry

[John Zenger]

On May 16, 11:21 am, Lisa <[e-mail]:

I am reading in data from a text file. I want to enter each value on
the line into a list and retain the order of the elements. The number
of elements and spacing between them varies, but a typical line looks
like:

' SRCPARAM 1 6.35e-07 15.00 340.00 1.10 3.0 '

Why does the following not work:

line = ' SRCPARAM 1 6.35e-07 15.00 340.00 1.10 3.0 '
li = line.split(' ')
for j,i in enumerate(li):
if i == '':
li.remove(i)

After the original split I get:
['', '', '', 'SRCPARAM', '', '', '1', '6.35e-07', '15.00', '',
'340.00', '', '', '1.10', '', '', '', '', '', '3.0', '', '', '']

And after the for loop I get:
['SRCPARAM', '1', '6.35e-07', '15.00', '340.00', '1.10', '', '', '',
'3.0', '', '', '']

It doesn't remove all of the empty elements. Is there a better way to
split the original string? Or a way to catch all of the empty
elements?

Thanks

As explained elsewhere, this is not the best way to do a split. But
if in the future you run into the problem of how to remove all
elements in a list with a particular value, here are two popular
approaches:

>>items = ['', '', '', 'SRCPARAM', '', '', '1', '6.35e-07', '15.00', '',

'340.00', '', '', '1.10', '', '', '', '', '', '3.0', '', '', '']

>>print filter(lambda i: i != '', items)

['SRCPARAM', '1', '6.35e-07', '15.00', '340.00', '1.10', '3.0']

>>print [x for x in items if x != '']

['SRCPARAM', '1', '6.35e-07', '15.00', '340.00', '1.10', '3.0']

[Lisa]

Great. Thanks for your help.

[James Stroud]

John Zenger wrote:

>>>>print [x for x in items if x != '']

['SRCPARAM', '1', '6.35e-07', '15.00', '340.00', '1.10', '3.0']

This can be shortened to

[x for x in items if x]

James

[MRAB]

On May 16, 4:21 pm, Lisa <[e-mail]:

I am reading in data from a text file. I want to enter each value on
the line into a list and retain the order of the elements. The number
of elements and spacing between them varies, but a typical line looks
like:

' SRCPARAM 1 6.35e-07 15.00 340.00 1.10 3.0 '

Why does the following not work:

line = ' SRCPARAM 1 6.35e-07 15.00 340.00 1.10 3.0 '
li = line.split(' ')
for j,i in enumerate(li):
if i == '':
li.remove(i)

[snip]
What you're forgetting is that when you remove an item from a list all
the following items move down.

If you try this:

li = list('abc')
for i, j in enumerate(li):
print ", ".join("li[%d] is '%s'" % (p, q) for p, q in
enumerate(li))
print "Testing li[%d], which is '%s'" % (i, j)
if j == 'a':
print "Removing '%s' from li" % j
li.remove(j)

then you'll get:

li[0] is 'a', li[1] is 'b', li[2] is 'c'
Testing li[0], which is 'a'
Removing 'a' from li
li[0] is 'b', li[1] is 'c'
Testing li[1], which is 'c'

You can see that when 'enumerate' yielded li[0] 'b' was in li[1] and
when it yielded li[1] 'b' was in li[1]; it never saw 'b' because 'b'
moved!

Oops! Been there, done that... :-)

[Steven Howe]

Steven Howe wrote:

MRAB wrote:

>On May 16, 4:21 pm, Lisa <[e-mail]<mailto:lisa.engb...@gmail. comwrote:

I am reading in data from a text file. I want to enter each value on
the line into a list and retain the order of the elements. The number
of elements and spacing between them varies, but a typical line looks
like:

' SRCPARAM 1 6.35e-07 15.00 340.00 1.10 3.0 '

Using builtin functions:

ax = ' SRCPARAM 1 6.35e-07 15.00 340.00 1.10 3.0 '

>>ax.replace(' ','') # replace all double spaces with nothing

' SRCPARAM 1 6.35e-07 15.00340.00 1.103.0 '

>>ax.replace(' ','').strip() # strip leading/trailing white spaces

'SRCPARAM 1 6.35e-07 15.00340.00 1.103.0'

>>ax.replace(' ','').strip().split(' ') # split string into a

list, using remaining white space as key
['SRCPARAM', '1', '6.35e-07', '15.00340.00', '1.103.0']

def getElements( str ):
return str.replace( ' ', '' ).strip().split(' ')
sph

Made a mistake in the above code. Works well so long as there are no
double spaces in the initial string.
Try 2:
def compact( y ):
if y.find(' ') == -1:
return y
else:
y = y.replace( ' ', ' ' )
return compact( y )

>>ax = ' acicd 1.345 aex a;dae '
print compact( ax )

acicd 1.345 aex a;dae

>>print compact( ax ).strip().split()

['acicd', '1.345', 'aex', 'a;dae']

sph

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HEX: 09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0