Archive:Python/Operators: Difference between revisions
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==Indexing== | ==Indexing== | ||
You have already learned how to index in lesson 2. When you typed x[3] you where indexing. You may also index a string without first making a variable represent it. | |||
Type: | |||
>>>'''"I Love Wikipedia"'''[5] | |||
'''e''' | |||
simple enough. | |||
===Slicing=== | |||
''Slicing'' is used to access a range of elements the way that ''indexing'' accessess one element. | |||
Type: | |||
>>>'''x = "Wikipedia and Python are awesome"''' | |||
Now Type: | |||
>>>'''print x[14:32] | |||
'''Python are awesome''' | |||
The numbers that you enter after the variable (the [14:32]) are called ''indices''. The way the last one works is hard to understand at first. I'll do another example to make it clear. | |||
Type: | |||
>>>'''x = '1234'''' | |||
Now type: | |||
'''print x[1:3]'''' | |||
'''23''' | |||
It prints out the 2 because it starts numbering at 0, but the reason it prints out the 3 instead of the 4 is because it counts the '''[3]''' that you entered as the end point and does not include it. Seems wierd at first but easy to get used to. | |||
You may also use negative numbers as the indices '''(x[-12:-])'''. If you only use one negative indice '''(x[-4:])''' Python will print starting with the element selected and go until the end of the string, tuple or list. This works for positive indices as well '''(x[:3])'''. Python will print the first 2 elements of '''x'''. | |||
Another thing that you can do when ''splicing'' is enter the ''step'' indice. | |||
Type: | |||
>>>'''x = "0123456789"''' | |||
Now Type: | |||
>>>'''x[1:-1:3]''' | |||
''' '147' ''' | |||
== | |||