5. Dictionaries

• The dictionary itself consists of relating a key with a specific value

• Unlike lists, where the index is a number, dictionaries use their keys as index

• To add new elements that I don’t need to add, just make the session

  • If the key already exists: the associated value changes

  • If the key does not exist: the new key is added

1 d = {} 2 d["a"] = "alpha" 3 d["o"] = "omega" 4 d["g"] = "gamma" 5 print(d) 6 print(d["a"]) Edit this code line that just executed next line to execute << First < Prev Next > Last >> Step 1 of 6 Submit Python Tutor by Philip Guo Customize visualization (NEW!)

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Activity: CodeLens 5.1 (cl_l23_5a_en)

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1

d = {}

2

d["a"] = "alpha"

3

d["o"] = "omega"

4

d["g"] = "gamma"

5

print(d)

6

​

7

​

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# This line will result in an error because there is no

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# a "x" key in the dictionary

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print(d["x"])

11

​

Activity: 5.2 ActiveCode (ac_l23_5_en)

1 d = {} 2 d["a"] = "alpha" 3 d["o"] = "omega" 4 d["g"] = "gamma" 5 print(d.keys()) 6 print(d.values()) 7 print("g" in d) 8 print("x" in d) 9 for key in d: 10     print(key) Edit this code line that just executed next line to execute << First < Prev Next > Last >> Step 1 of 15 Submit Python Tutor by Philip Guo Customize visualization (NEW!)

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Activity: CodeLens 5.3 (cl_l23_5b_en)

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