{:.no_toc}
* TOC {:toc}Lists are mutable sequences, typically used to store collections of homogeneous items (where the precise degree of similarity will vary by application).
Questions to David Rotermund
With homogeneous items:
primes = [2, 3, 5, 7]
collection_of_strings = [
"AA",
"BB",
"CC",
"DD",
"EE",
"FF",
"GG",
"HH",
]
A mixture of type:
def my_function(a):
return a
my_favourite_things = [32, "sleep", my_function]
collection_of_strings = [
"AA",
"BB",
"CC",
"DD",
"EE",
"FF",
"GG",
"HH",
]
print(collection_of_strings[0]) # -> AA
print(collection_of_strings[1]) # -> BB
print(collection_of_strings[-2]) # -> GG
print(collection_of_strings[-1]) # -> HH
collection_of_strings = [
"AA",
"BB",
"CC",
"DD",
"EE",
"FF",
"GG",
"HH",
]
print(collection_of_strings[0:3]) # -> ['AA', 'BB', 'CC']
print(collection_of_strings[:3]) # -> ['AA', 'BB', 'CC']
print(collection_of_strings[3:]) # -> ['DD', 'EE', 'FF', 'GG', 'HH']
print(collection_of_strings[1:-1]) # -> ['BB', 'CC', 'DD', 'EE', 'FF', 'GG']
print(collection_of_strings[-3:]) # -> ['FF', 'GG', 'HH']
print(collection_of_strings[0:3]) # -> ['AA', 'BB', 'CC']
print(collection_of_strings[0:3:1]) # -> ['AA', 'BB', 'CC']
print(collection_of_strings[0:3:2]) # -> ['AA', 'CC']
print(collection_of_strings[::2]) # -> ['AA', 'CC', 'EE', 'GG']
collection_of_strings = [
"AA",
"BB",
"CC",
"DD",
"EE",
"FF",
"GG",
"HH",
]
collection_of_strings[3] = "II"
print(collection_of_strings) # -> ['AA', 'BB', 'CC', 'II', 'EE', 'FF', 'GG', 'HH']
collection_of_strings[:3] = ["JJ", "KK", "LL"]
print(collection_of_strings) # -> ['JJ', 'KK', 'LL', 'II', 'EE', 'FF', 'GG', 'HH']
collection_of_strings[:4] = [
"MM",
"NN",
"OO",
"PP",
]
print(collection_of_strings) # -> ['MM', 'NN', 'OO', 'PP', 'EE', 'FF', 'GG', 'HH']
collection_of_strings = [
"GG",
"HH",
"AA",
"BB",
"EE",
"FF",
"CC",
"DD",
]
print(len(collection_of_strings)) # -> 8
print(sorted(collection_of_strings)) # -> ['AA', 'BB', 'CC', 'DD', 'EE', 'FF', 'GG', 'HH']
primes = [2, 3, 5, 7]
print(sum(primes)) # -> 17
print(max(primes)) # -> 7
print(min(primes)) # -> 2
Is x in list?
collection_of_strings = [
"AA",
"BB",
"CC",
"DD",
"EE",
"FF",
"GG",
"HH",
]
print("AA" in collection_of_strings) # -> True
print("XX" in collection_of_strings) # -> False
print("AA" not in collection_of_strings) # -> False
print("XX" not in collection_of_strings) # -> True
Which index id has an element in a list?
collection_of_strings = [
"AA",
"BB",
"CC",
"DD",
"EE",
"FF",
"GG",
"HH",
]
print(collection_of_strings.index("CC")) # -> 2
print(collection_of_strings.index("XX")) # -> ValueError: 'XX' is not in list
Maybe we don't want to start in the beginning of the list or don't want to search until the end of the list:
collection_of_strings = [
"AA",
"BB",
"CC",
"DD",
"EE",
"BB",
"FF",
"GG",
"BB",
"HH",
]
print(collection_of_strings.index("BB")) # -> 1
# At or after 2
print(collection_of_strings.index("BB", 2)) # -> 5
# Before 6
print(collection_of_strings.index("BB", 2, 6)) # -> 5
# Before 4
print(collection_of_strings.index("BB", 2, 4)) # ValueError: 'BB' is not in list
collection_of_strings = [
"AA",
"BB",
"BB",
"CC",
"DD",
"EE",
"FF",
"GG",
"HH",
]
collection_of_strings.append("II")
print(
collection_of_strings
) # -> ['AA', 'BB', 'BB', 'CC', 'DD', 'EE', 'FF', 'GG', 'HH', 'II']
print(collection_of_strings.pop()) # -> II
print(
collection_of_strings
) # -> ['AA', 'BB', 'BB', 'CC', 'DD', 'EE', 'FF', 'GG', 'HH']
collection_of_strings.remove("BB")
print(collection_of_strings) # -> ['AA', 'BB', 'CC', 'DD', 'EE', 'FF', 'GG', 'HH']
collection_of_strings.remove("BB")
print(collection_of_strings) # -> ['AA', 'BB', 'CC', 'DD', 'EE', 'FF', 'GG', 'HH']
collection_of_strings.remove("BB")
print(collection_of_strings) # -> ValueError: list.remove(x): x not in list
Insert and delete an element.
collection_of_strings = []
collection_of_strings.append("BB")
collection_of_strings.append("CC")
collection_of_strings.append("DD")
print(collection_of_strings) # -> ['BB', 'CC', 'DD']
collection_of_strings.insert(0, "AA")
print(collection_of_strings) # -> ['AA', 'BB', 'CC', 'DD']
del collection_of_strings[1]
print(collection_of_strings) # -> ['AA', 'CC', 'DD']
Concatenating lists.
collection_of_strings_a = [
"AA",
"BB",
"CC",
"DD",
]
collection_of_strings_b = [
"EE",
"FF",
"GG",
"HH",
]
print(collection_of_strings_a) # -> ['AA', 'BB', 'CC', 'DD']
print(collection_of_strings_b) # -> ['EE', 'FF', 'GG', 'HH']
collection_of_strings = collection_of_strings_a + collection_of_strings_b
print(collection_of_strings) # -> ['AA', 'BB', 'CC', 'DD', 'EE', 'FF', 'GG', 'HH']
Repeat a list several times.
collection_of_strings = [
"AA",
"BB",
"CC",
]
print(3 * collection_of_strings) # -> ['AA', 'BB', 'CC', 'AA', 'BB', 'CC', 'AA', 'BB', 'CC']
print(collection_of_strings * 3) # -> ['AA', 'BB', 'CC', 'AA', 'BB', 'CC', 'AA', 'BB', 'CC']
How often does an element occur in the list?
collection_of_strings = [
"AA",
"AA",
"BB",
"BB",
"BB",
"CC",
"DD",
"EE",
"FF",
"GG",
"HH",
]
print(collection_of_strings.count("AA")) # -> 2
print(collection_of_strings.count("BB")) # -> 3
print(collection_of_strings.count("CC")) # -> 1
list.append(x) |
list.extend(iterable) |
list.insert(i, x) |
list.remove(x) |
list.pop([i]) |
list.clear() |
list.index(x[, start[, end]]) |
list.count(x) |
list.sort(*, key=None, reverse=False) |
list.reverse() |
list.copy() |
Operation | Result |
---|---|
x in s | True if an item of s is equal to x, else False |
x not in s | False if an item of s is equal to x, else True |
s + t | the concatenation of s and t |
s * n or n * s | equivalent to adding s to itself n times |
s[i] | ith item of s, origin 0 |
s[i:j] | slice of s from i to j |
s[i:j:k] | slice of s from i to j with step k |
len(s) | length of s |
min(s) | smallest item of s |
max(s) | largest item of s |
s.index(x[, i[, j]]) | index of the first occurrence of x in s (at or after index i and before index j) |
s.count(x) | total number of occurrences of x in s |