How do I slice a python string programmatically?

Question

Very simple question, hopefully. So, in Python you can split up strings using indices as follows:

>>> a="abcdefg"
>>> print a[2:4]
cd

but how do you do this if the indices are based on variables? E.g.

>>> j=2
>>> h=4
>>> print a[j,h]
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
TypeError: string indices must be integers

Use a colon, not a comma ... just like you would with numerical indices. :o) — Johannes Charra
– Johannes Charra, Commented May 27, 2010 at 11:15

bakkal · Accepted Answer · 2010-05-27 11:16:57Z

12

It works you just have a typo in there, use a[j:h] instead of a[j,h] :

>>> a="abcdefg"
>>> print a[2:4]
cd
>>> j=2
>>> h=4
>>> print a[j:h]
cd
>>>

answered May 27, 2010 at 11:16

bakkal

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Comments

Olivier Verdier · Accepted Answer · 2010-05-27 11:27:49Z

5

In addition to Bakkal's answer, here is how to manipulate slices programmatically, which is sometimes convenient:

a = 'abcdefg'
j=2;h=4
my_slice = slice(j,h) # you can pass this object around if you wish

a[my_slice] # -> cd

answered May 27, 2010 at 11:27

Olivier Verdier

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