Strings
Table of contents
Description
Strings are simply a sequence of characters, enclosed by quotes.
- Immutable: you cannot change the values of their individual characters.
- Index numbers allow access to individual characters.
- Ordered: The characters are stored in a specific order.
- Many different actions (methods and functions) can be performed on strings.
- Python Docs: Strings, Text Sequence Type
Example
Indexing
An index is the position of an element in a sequence. Indexing begins at 0 with the first element. Negative indexing begins at -1 with the last element.
Slicing
A slice is a piece of a string. It is defined by a starting index, a (non-inclusive) ending index, and a step value. If any of the three arguments to the slice are missing, the defaults are as follows:
- Start: first character
- End: last character
- Step: 1
| Start | End + 1 | Step | Code | Result |
|---|---|---|---|---|
| 3 | 9 | flavor[3:9] | ‘ten La’ | |
| 6 | flavor[:6] | ‘Molten’ | ||
| 7 | flavor[7:] | ‘Lava’ | ||
flavor[:] | ‘Molten Lava’ | |||
| -1 | -1 | flavor[-1::-1] | ‘avaL netloM’ | |
| 2 | flavor[::2] | ‘Mle aa’ |
Immutability
Strings are immutable. This means once you instantiate them, you can’t change their attributes.
- Run the program as-is, with line 5 commented out. Notice the error in the console:
'str' object does not support item assignment.
- Next, comment out line 4, and uncomment line 5. The program will run without any errors.
So, you can reassign an entire string, but you cannot reassign parts (individual elements) of a string.