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What this code will output and why? - Valgard - Aug-30-2017
Today I meet this exercise:
What this code will output and why?
x = [[]]*3
x[0].append('a')
x[1].append('b')
x[2].append('c')
x[0]=['d']
print(x) I expected to see 'd b c', but whet i run this program i was surprised. The output is [['d'], ['a', 'b', 'c'], ['a', 'b', 'c']].
Why is this code works this way?
RE: What this code will output and why? - BerlingSwe - Aug-30-2017
Brcause you are using a 2 dimensional list. Play around with it for a bit and I'm sure you will understand! :)
a = [[1, 2, 3], [4, 5, 6], [7, 8, 9]] print(a[0]) print(a[0][1])Try this code and experiment with it by printing, removing, appending etc
RE: What this code will output and why? - dwiga - Aug-30-2017
Output:[['d'], ['a', 'b', 'c'], ['a', 'b', 'c']]RE: What this code will output and why? - snippsat - Aug-30-2017
x = [[]]*3 this copy 3 list to same memory adress.>>> x = [[]]*3 >>> [id(i) for i in x] [57560800, 57560800, 57560800]Do it like this.
>>> x = [[] for i in range(3)] >>> [id(i) for i in x] [66352912, 66412416, 65766344]Then it look like this.
x = [[] for i in range(3)]
x[0].append('a')
x[1].append('b')
x[2].append('c')
x[0] = ['d']
print(x)Output:[['d'], ['b'], ['c']]RE: What this code will output and why? - Valgard - Aug-30-2017
Thank you for detailed answer. I will experiment with this python feature.