Split list python by index

How do I split a list into sub-lists based on index ranges?

e.g. original list:

list1 = [x,y,z,a,b,c,d,e,f,g]

using index ranges 0–4:

list1a = [x,y,z,a,b]

using index ranges 5–9:

list1b = [c,d,e,f,g]

I already known the (variable) indices of list elements which contain certain string and want to split the list based on these index values.

Also need to split into variable number of sub-lists, i.e.:

list1a
list1b
.
.
list1[x]

Split list python by index

mkrieger1

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asked Sep 2, 2013 at 10:15

Split list python by index

1

In python, it's called slicing. Here is an example of python's slice notation:

>>> list1 = ['a','b','c','d','e','f','g','h', 'i', 'j', 'k', 'l']
>>> print list1[:5]
['a', 'b', 'c', 'd', 'e']
>>> print list1[-7:]
['f', 'g', 'h', 'i', 'j', 'k', 'l']

Note how you can slice either positively or negatively. When you use a negative number, it means we slice from right to left.

answered Sep 2, 2013 at 10:20

Split list python by index

TerryATerryA

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1

Note that you can use a variable in a slice:

l = ['a',' b',' c',' d',' e']
c_index = l.index("c")
l2 = l[:c_index]

This would put the first two entries of l in l2

answered Sep 2, 2013 at 10:33

Split list python by index

0

If you already know the indices:

list1 = ['x','y','z','a','b','c','d','e','f','g']
indices = [(0, 4), (5, 9)]
print [list1[s:e+1] for s,e in indices]

Note that we're adding +1 to the end to make the range inclusive...

answered Sep 2, 2013 at 10:31

Split list python by index

Jon ClementsJon Clements

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list1a=list[:5]
list1b=list[5:]

answered Sep 2, 2013 at 10:17

no1no1

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5

One of the ways to do it if you have multiple indexes or know the range of indexes you need to get:

split_points - points where you will split your string or list

k - the range you need to split, example = 3

split_points = [i for i in range(0, len(string), k)]

parts = [string[ind:ind + k] for ind in split_points]

answered Apr 11, 2021 at 18:32

list1=['x','y','z','a','b','c','d','e','f','g']
find=raw_input("Enter string to be found")
l=list1.index(find)
list1a=[:l]
list1b=[l:]

answered Sep 2, 2013 at 10:28

no1no1

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0

Consider the core pesudocode of the following example:

def slice_it(list_2be_sliced, indices):
    """Slices a list at specific indices into constituent lists.
    """
    indices.append(len(list_2be_sliced))
    return [list_2be_sliced[indices[i]:indices[i+1]] for i in range(len(indices)-1)]

answered Mar 4, 2021 at 21:17

ShadyShady

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This is the way I do it, if the input is a list of indices on which to split an array:

#input
list1 = ['x','y','z','a','b','c','d','e','f','g']
split_points = [2,5,8] 

#split array on indices:
s = split_points+[len(list1)]  #must contain index beyond last element, alternatively use directly split_points.append(len(list1))
print([list1[i1:i2] for i1,i2 in zip([0]+s[:-1],s)])

>>> [['x', 'y'], ['z', 'a', 'b'], ['c', 'd', 'e'], ['f', 'g']]

answered Jun 27 at 16:37

Split list python by index

VincenzoooVincenzooo

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How do you split a specific index in Python?

Indexes in Python are zero-based, so the first item in a list has an index of 0 , the second an index of 1 , etc..
Use the str. split() method to split the string into a list..
Access the list element at the specific index..
Assign the result to a variable..

How do you split a list into two parts in Python?

This can be done using the following steps:.
Get the length of a list using len() function..
If the length of the parts is not given, then divide the length of list by 2 using floor operator to get the middle index of the list..
Slice the list into two halves using [:middle_index] and [middle_index:].

How do you split a list in a list Python?

To split the elements of a list in Python: Use a list comprehension to iterate over the list. On each iteration, call the split() method to split each string. Return the part of each string you want to keep.

How do you split a list into delimiter in Python?

The split() method of the string class is fairly straightforward. It splits the string, given a delimiter, and returns a list consisting of the elements split out from the string. By default, the delimiter is set to a whitespace - so if you omit the delimiter argument, your string will be split on each whitespace.

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