Python chapter 6 learning notes

  A simple dictionary

1 2	alien_0 = {'color': 'green','point': 5} print(alien_0['color'])#使用大括號

The window will show green.

l  Using dictionary

n  Add key-value pair

For example,

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alien_0 = {'color': 'green','point': 5} print(alien_0['color'])    alien_0['x_position'] = 0 alien_0['y_position'] = 25 print(alien_0)

The window will show

1	{'color': 'green', 'point': 5, 'x_position': 0, 'y_position': 25}

• • Modify the key-value pair

1	alien_0['color'] = 'yellow'

• • Delete the key-value pair

Use del is OK.

For example,

1	del alien_0['points']

Dictionary will not include points.

• • Dictionary just like struct in C language.

  • The dictionary which consists of many objects:

For example,

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favorite_languages = { 'David': 'python', 'Jane' : 'java', 'John' : 'C', 'Sarah' : 'ruby', 'Michel' : 'swift'  }    print("David's favorite languages is " +  favorite_languages['David'].title() + ".")

It will show,

1	David's favorite languages is Python.

Remember the format!

l  Ergodic dictionary

n  Ergodic all key-value pairs

Method: items(): items()方法用於返回字典dict的(key，value)元組對的列表

• • Ergodic all keys

Method: keys():返回字典dict的鍵列表

For example,

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for name in favorite_languages.keys(): print(name.title() +  ".") But if we use for name in favorite_languages: print(name.title() +  ".")

They all have same output.

n  Ergodic all values

n  Method: values():返回字典dict的值列表

As we all know, the list of value may have same values, then ,how to keep only one value?

We can use set(). For example,

1 2	for language in set(favorite_languages.values()): print(language.title())

n  Nesting: 將一系列字典存儲在列表中，或將列表作爲值存儲在字典中，這被稱爲嵌套。