Deleting elements with specific substring in python

Question

I have a list with many elements that I have extracted from an html page using Beautiful Soup. Within this list I have many elements with the same substring, and I would like to extract every element that contains that substring.

My list looks like:

[
u'File:Saddam Hussein (107).jpg',
u'Template:Fn (page does not exist)',
u'Template:Fn (page does not exist)',
u'Template:Fn (page does not exist)',
u'Template:Fn (page does not exist)',
u'Template:Fn (page does not exist)',
u'File:AlBakr.jpg',
... (and so on) ...
]

And I would like to delete and element that has the string "(page does not exist)".

Any thoughts on how I could do this?

Ashwini Chaudhary · Accepted Answer · 2013-06-25 17:50:43Z

2

Use a list comprehension:

>>> lis = [u'File:Saddam Hussein (107).jpg', u'Template:Fn (page does not exist)', u'Template:Fn (page does not exist)', u'Template:Fn (page does not exist)', u'Template:Fn (page does not exist)', u'Template:Fn (page does not exist)', u'File:AlBakr.jpg', u'Template:Fn (page does not exist)', u'File:Chiracsaddam.jpg', u'File:Donald saddam.jpg', u'Template:Fn (page does not exist)', u'File:SaddamandCuellar.jpg.jpg', u'Template:Fn (page does not exist)', u'Template:Fn (page does not exist)', u'File:SaddamBaghdadwalkabout.jpg', u'Template:Fn (page does not exist)', u'Template:Fn (page does not exist)', u'Template:Fn (page does not exist)', u'Kurdish Patriotic Front (page does not exist)', u'File:TrialSaddam.jpg', u'Mohammad Rashdan (page does not exist)', u'Emmanuel Ludot (page does not exist)', u'Marc Henzelin (page does not exist)', u'Adnan Khairallah Tuffah (page does not exist)', u'Nidal al-Hamdani (page does not exist)', u'Ali Hussein (page does not exist)', u'File:SaddamandRana.jpg.jpg', u'Saddam Kamel Majid (page does not exist)', u'Template:Fn (page does not exist)', u'Template:Fnb (page does not exist)', u'Template:Fnb (page does not exist)', u'Template:Fnb (page does not exist)', u'Template:Fnb (page does not exist)', u'Template:Fnb (page does not exist)', u'Template:Fnb (page does not exist)', u'Template:Fnb (page does not exist)', u'Template:Fnb (page does not exist)', u'Template:Fnb (page does not exist)', u'Template:Fnb (page does not exist)', u'Template:Fnb (page does not exist)', u'Template:Fnb (page does not exist)', u'Template:Fnb (page does not exist)']

If you want to modify the original list:

>>> lis[:] = [item for item in lis if "(page does not exist)" not in item]

Or to create a new list:

new_lis = [item for item in lis if "(page does not exist)" not in item]

answered Jun 25, 2013 at 17:50

Ashwini Chaudhary

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5 Comments

John Over a year ago

Why the copy, [:]? I'm pretty sure that's unnecessary.

Ashwini Chaudhary Over a year ago

@johnthexiii lis[:] is not a copy, see stackoverflow.com/questions/11297774/…

John Over a year ago

@AshwiniChaudhary, perhaps a better question is why keep the original reference? I am not implying that it is a bad thing, I'm just curios.

Ashwini Chaudhary Over a year ago

@johnthexiii OP mentioned "would like to delete", so I provided both alternatives. That's the only reason.

jfs Over a year ago

@johnthexiii: sometimes the change should be inplace e.g., os.walk() allows to manipulate what directories are visited by changing dirs list.

Steve Barnes · Accepted Answer · 2013-06-25 17:55:00Z

0

>>> for i in range(len(l)-1, 0, -1):
...    if l[i].find('(page does not exist)') > -1:
...       del (l[i])
...
>>> l
[u'File:Saddam Hussein (107).jpg']
>>>

answered Jun 25, 2013 at 17:55

Steve Barnes

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2 Comments

Cristian Ciupitu Over a year ago

del l[i]- you don't need the parentheses. Also L is a better variable name than l.

Ashwini Chaudhary Over a year ago

Note that del and pop are expensive operations for lists.(pop is slightly faster than del)

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