# Lists

* List consist of a sequnece of different types delimited by square barckets \[ and ]
* Unlike strings which only contain characters, list elements can be anything, including other lists

```
In [1]: alist=['The','principal','author','of','Python','is',['Guido','van','Rossum']]

In [2]: alist[6]
Out[2]: ['Guido', 'van', 'Rossum']

In [3]: alist[6][0]
Out[3]: 'Guido'
```

* lists are mutable and strings are immutable

```
In [4]: alist[1]='first'

In [5]: alist
Out[5]: ['The', 'first', 'author', 'of', 'Python', 'is', ['Guido', 'van', 'Rossum']]

In [6]: astring="Van Rossum is a big fan of Monty Python's Flying Circus"

In [7]: astring[1]='x'
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
/net/rowley/ifs/data/bcc/duan/test_python/<ipython-input-7-7abb36ddd2dd> in <module>()
----> 1 astring[1]='x'

TypeError: 'str' object does not support item assignment

```

* We can grow lists in several ways - using insert, append and list concatenation

```
In [8]: blist=['Python','was','conceived','in','1989']

In [9]: blist
Out[9]: ['Python', 'was', 'conceived', 'in', '1989']

In [10]: blist.append('around Christmas')

In [11]: blist
Out[11]: ['Python', 'was', 'conceived', 'in', '1989', 'around Christmas']

In [12]: blist=blist+["as","a","hobby","project"]

In [13]: blist
Out[13]: 
['Python',
 'was',
 'conceived',
 'in',
 '1989',
 'around Christmas',
 'as',
 'a',
 'hobby',
 'project']

In [14]: blist[4:4]=["December",]

In [15]: blist
Out[15]: 
['Python',
 'was',
 'conceived',
 'in',
 'December',
 '1989',
 'around Christmas',
 'as',
 'a',
 'hobby',
 'project']

```

* We can remove items from a list by using pop, del or assigning a slice to the empty list

```
In [16]: blist.pop()
Out[16]: 'project'
In [17]: blist
Out[17]: 
['Python',
 'was',
 'conceived',
 'in',
 'December',
 '1989',
 'around Christmas',
 'as',
 'a',
 'hobby']

In [18]: del blist[4]

In [19]: blist
Out[19]: 
['Python',
 'was',
 'conceived',
 'in',
 '1989',
 'around Christmas',
 'as',
 'a',
 'hobby']

In [20]: del blist[6:9]

In [21]: blist
Out[21]: ['Python', 'was', 'conceived', 'in', '1989', 'around Christmas']

In [22]: blist[3:5]=[]

In [22]: blist
Out[22]: ['Python', 'was', 'conceived', 'around Christmas']
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://igb.mit.edu/mini-courses/python/introduction-to-python-for-biologists/types/lists.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.