171 lines
3.2 KiB
Markdown
171 lines
3.2 KiB
Markdown
# Sequence Types: list
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{:.no_toc}
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<nav markdown="1" class="toc-class">
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* TOC
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{:toc}
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</nav>
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## The goal
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> Lists are **mutable** sequences, **typically** used to store collections of **homogeneous** items (where the precise degree of similarity will vary by application).
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[Quote](https://docs.python.org/3/library/stdtypes.html#lists)
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Questions to [David Rotermund](mailto:davrot@uni-bremen.de)
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## Example Lists
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With homogeneous items:
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```python
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primes = [2, 3, 5, 7]
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collection_of_strings = [
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"AA",
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"BB",
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"CC",
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"DD",
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"EE",
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"FF",
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"GG",
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"HH",
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]
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```
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A mixture of type:
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```python
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def my_function(a):
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return a
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my_favourite_things = [32, "sleep", my_function]
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```
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## Indexing
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```python
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collection_of_strings = [
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"AA",
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"BB",
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"CC",
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"DD",
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"EE",
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"FF",
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"GG",
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"HH",
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]
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print(collection_of_strings[0]) # -> AA
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print(collection_of_strings[1]) # -> BB
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print(collection_of_strings[-2]) # -> GG
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print(collection_of_strings[-1]) # -> HH
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```
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## Slicing
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```python
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collection_of_strings = [
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"AA",
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"BB",
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"CC",
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"DD",
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"EE",
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"FF",
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"GG",
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"HH",
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]
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print(collection_of_strings[0:3]) # -> ['AA', 'BB', 'CC']
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print(collection_of_strings[:3]) # -> ['AA', 'BB', 'CC']
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print(collection_of_strings[3:]) # -> ['DD', 'EE', 'FF', 'GG', 'HH']
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print(collection_of_strings[1:-1]) # -> ['BB', 'CC', 'DD', 'EE', 'FF', 'GG']
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print(collection_of_strings[-3:]) # -> ['FF', 'GG', 'HH']
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```
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## Changing lists
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```python
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collection_of_strings = [
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"AA",
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"BB",
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"CC",
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"DD",
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"EE",
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"FF",
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"GG",
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"HH",
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]
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collection_of_strings[3] = "II"
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print(collection_of_strings) # -> ['AA', 'BB', 'CC', 'II', 'EE', 'FF', 'GG', 'HH']
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collection_of_strings[:3] = ["JJ", "KK", "LL"]
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print(collection_of_strings) # -> ['JJ', 'KK', 'LL', 'II', 'EE', 'FF', 'GG', 'HH']
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collection_of_strings[:4] = [
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"MM",
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"NN",
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"OO",
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"PP",
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]
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print(collection_of_strings) # -> ['MM', 'NN', 'OO', 'PP', 'EE', 'FF', 'GG', 'HH']
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```
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## List functions
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### [len()](https://docs.python.org/3/library/functions.html#len) and [sorted()](https://docs.python.org/3/library/functions.html#sorted)
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```python
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collection_of_strings = [
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"GG",
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"HH",
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"AA",
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"BB",
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"EE",
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"FF",
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"CC",
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"DD",
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]
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print(len(collection_of_strings)) # -> 8
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print(sorted(collection_of_strings)) # -> ['AA', 'BB', 'CC', 'DD', 'EE', 'FF', 'GG', 'HH']
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```
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### [max()](https://docs.python.org/3/library/functions.html#max) and [sum()](https://docs.python.org/3/library/functions.html#sum)
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```python
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primes = [2, 3, 5, 7]
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print(sum(primes)) # -> 17
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print(max(primes)) # -> 7
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```
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### [append()](), [pop()](), and [remove()]()
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```python
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collection_of_strings = [
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"AA",
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"BB",
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"BB",
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"CC",
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"DD",
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"EE",
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"FF",
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"GG",
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"HH",
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]
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collection_of_strings.append("II")
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print(
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collection_of_strings
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) # -> ['AA', 'BB', 'BB', 'CC', 'DD', 'EE', 'FF', 'GG', 'HH', 'II']
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print(collection_of_strings.pop()) # -> II
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print(
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collection_of_strings
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) # -> ['AA', 'BB', 'BB', 'CC', 'DD', 'EE', 'FF', 'GG', 'HH']
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collection_of_strings.remove("BB")
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print(collection_of_strings) # -> ['AA', 'BB', 'CC', 'DD', 'EE', 'FF', 'GG', 'HH']
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```
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