On 05/30/2014 08:38 PM, Josh English wrote:
...
def zero_matrix(rows, cols):
row = [0] * cols
data = []
for r in range(rows):
data.append(row)
return Matrix(data)
There is a simple and common newbie mistake here. It looks like you
are appending several copies of a zero row to data, but in fact you are
appending multiple references to a single row. (The hint is that you
only created *one* row.)
Put the
row = [0] * cols
inside the loop so each append is using its own row rather than one
shared row being used multiple times.
Here's a small example that demonstrates problem:
>>> row = [0,0,0,0]
>>> data = []
>>> data.append(row)
>>> data.append(row)
>>> data[0][0] = 99
>>> data
[[99, 0, 0, 0], [99, 0, 0, 0]]
Gary Herron
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