Lists (Python)
Een list is hetzelfde als een array.
Voorbeeld Wikibooks
[1]:
<source lang="python"> list1 = [] # A new empty list list2 = [1, 2, 3, "cat"] # A new non-empty list with mixed item types list1.append("cat") # Add a single member, at the end of the list list1.extend(["dog", "mouse"]) # Add several members list1.insert(0, "fly") # Insert at the beginning list1[0:0] = ["cow", "doe"] # Add members at the beginning doe = list1.pop(1) # Remove item at index if "cat" in list1: # Membership test
list1.remove("cat") # Remove AKA delete
- list1.remove("elephant") - throws an error
for item in list1: # Iteration AKA for each item
print item
print "Item count:", len(list1) # Length AKA size AKA item count list3 = [6, 7, 8, 9] for i in range(0, len(list3)): # Read-write iteration AKA for each item
list3[i] += 1 # Item access AKA element access by index
last = list3[-1] # Last item nextToLast = list3[-2] # Next-to-last item isempty = len(list3) == 0 # Test for emptiness set1 = set(["cat", "dog"]) # Initialize set from a list list4 = list(set1) # Get a list from a set list5 = list4[:] # A shallow list copy list4equal5 = list4==list5 # True: same by value list4refEqual5 = list4 is list5 # False: not same by reference list6 = list4[:] del list6[:] # Clear AKA empty AKA erase list7 = [1, 2] + [2, 3, 4] # Concatenation print list1, list2, list3, list4, list5, list6, list7 print list4equal5, list4refEqual5 print list3[1:3], list3[1:], list3[:2] # Slices print max(list3 ), min(list3 ), sum(list3) # Aggregates
print [x for x in range(10)] # List comprehension print [x for x in range(10) if x % 2 == 1] print [x for x in range(10) if x % 2 == 1 if x < 5] print [x + 1 for x in range(10) if x % 2 == 1] print [x + y for x in '123' for y in 'abc'] </source>
Eigen probeersels
>>> lijst=[1, 2, 3, 4] # Je kunt een lijst gelijk initialiseren + van waardes voorzien
>>> print(lijst) # Zonder haakjes, worden alle elementen weergegven
[1, 2, 3, 4]
>>> print(len(lijst)) # Hoeveel elementen heeft een lijst?
4
>>> print(lijst[1]) # Verwijs naar elementen met rechte haakjes + index start bij 0
2
>>> lijst=[] # Zo initiëer je een lege lijst
>>> lijst[2] = "hoi" # Dat werkt niet! Je kunt geen elementen initiëren op deze manier
>>> lijst.append("hoi") # Dit werkt wel