Iterate over a dictionary

Iterate over a dictionary means iterate over the keys in the dictionary, we can use for loop to iterate over the keys in a dictionary.

d = {'apple':'red', 'pear':'green', 'banana':'yellow', 'plum':'purple'}

for k in d:
    print(k, 'is ', d[k])

run...

apple is red
pear is green
banana is yellow
plum is purple     # (the order may be different)

here in the for loop, k means the keys of dictionary d ('apple', 'pear'...); while d[k] means the value paired with the key k (they are 'red', 'green'...)

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Use dictionary in CodeCraft

Use dictionary to store (x,y) coordinates in CodeCraft

xh = {1:3, 2:6, 3:9}    # x:h pairs
for k in xh:
    column(key, -20, xh[k], 2)

The above app will build some cobblestone columns at x: 1,2,3 with corresponding height h: 3,6,9.

For your understanding:

Exercise 1

Continue with the above app, see if you understand the following code:

for k in xh:
  for i in range(key):
    block(i, xh[k], -20, 1)

Did you get the same horizontal brick lines with length of 1,2,3 at vertical locations 3,6,9? See the picture.

Exercise 2

If you call on function column() instead of block() in the same nesting loops, what do you expect? Guess before check out the following code and picture.

for k in xh:
  for i in range(k):
    column(i, (-20-i), xh[k], 1)

We vary the z value a little so all the structures will show up at different z layers. See in pic??, we get 3 sheets of blocks, width x, height y.

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