I’m YouKoutaku. These codes are from the book python_Crash_Course, 2nd edition. I learned python and took these notes for this book.
6.Dictionary
A datatype that has the key-value.
6.1 sample
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| alien = {'color': 'green', 'points': 5}
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6.2 using dictionary
6.2.1 check value in dictionary
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| alien = {'color': 'green', 'points': 5}
print(alien['color'])
print(alien['points'])
new_points = alien['points']
print(f"New points {new_points}")
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| green
5
New points 5
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6.2.2 add key in dictionary
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| alien = {'color': 'green', 'points': 5}
alien['xp'] = 0
alien['yp'] = 25
print(alien)
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| {'color': 'green', 'points': 5, 'xp': 0, 'yp': 25}
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6.2.3 empty dictionary
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| alien = {}
print(alien)
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6.2.4 change key in dictionary
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| alien = {'color': 'green', 'points': 5}
alien['color'] = 'yellow'
print(alien)
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| {'color': 'yellow', 'points': 5}
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6.2.5 deletee key in dictionary
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| alien = {'color': 'green', 'points': 5}
print(alien)
del alien['points']
print(alien)
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| {'color': 'green', 'points': 5}
{'color': 'green'}
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6.2.6 dictionary made by object
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| favorite_languages = {
'jen': 'python',
'sarah': 'c',
'edward': 'ruby',
'phil': 'python',
}
language = favorite_languages['sarah'].title()
print(f"Sarah's favorite language is {language}.")
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| Sarah's favorite language is C.
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6.2.7 using get() to check value
get(key_name, message when the key is't exist)
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| # not exist dict
alien_0 = {'color': 'green', 'speed': 'slow'}
print(alien_0['points'])
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| ---------------------------------------------------------------------------
KeyError Traceback (most recent call last)
Input In [11], in <cell line: 3>()
1 # not exist dict
2 alien_0 = {'color': 'green', 'speed': 'slow'}
----> 3 print(alien_0['points'])
KeyError: 'points'
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| #To avoid error
alien_0 = {'color': 'green', 'speed': 'slow'}
point_value = alien_0.get('points', 'No point value assigned.')
print(point_value)
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| No point value assigned.
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| # E-6-1
p ={
'first_name': "Y",
'last_name': "N",
'age': 18,
'city': "Tokyo"
}
print(p['first_name'],p['last_name'],p['age'],p['city'])
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6.3 check dictionary by for
6.3.1 key-value
dictionary.item()
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| user_0 = {
'username': 'david',
'first': 'enrico',
'last': 'fermi',
}
for key, value, in user_0.items():
print(f"\neKey:{key}")
print(f"Value:{value}")
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| eKey:username
Value:anny
eKey:first
Value:enrico
eKey:last
Value:fermi
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6.3.key
for a in dictionary = for a in dictionary.keys()
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| favorite_languages = {
'jen': 'python',
'sarah': 'c',
'edward': 'ruby',
'phil': 'python',
}
for name in favorite_languages:
print(name.title())
for name in favorite_languages.keys():
print(name.title())
#same
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| Jen
Sarah
Edward
Phil
Jen
Sarah
Edward
Phil
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| # using value by key in for
friends = ['phil', 'sarah']
for name in favorite_languages.keys():
print(f"Hi {name.title()}.")
if name in friends:
language = favorite_languages[name].title()
print(f"\t{name.title()}, I see you love {language}!")
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| Hi Jen.
Hi Sarah.
Sarah, I see you love C!
Hi Edward.
Hi Phil.
Phil, I see you love Python!
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| # not exist
if 'erin' not in favorite_languages.keys():
print("Erin, please take our poll!")
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| Erin, please take our poll!
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6.3.4 check all of value in dictionary by for
dictionary.values()
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| favorite_languages = {
'jen': 'python',
'sarah': 'c',
'edward': 'ruby',
'phil': 'python',
}
print("The following languages have been mentioned:")
for language in favorite_languages.values():
print(language.title())
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| The following languages have been mentioned:
Python
C
Ruby
Python
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| # when many values are in dictionary, We need to avoid the same value by using "set()"
for language in set(favorite_languages.values()):
print(language.title())
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| # create the set that means repeated value
language = {'python', 'ruby', 'c', 'python'}
language
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| {'c', 'python', 'ruby'}
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6.4 Nesting
create dictionary which have the value as list or create list which have the value as dictionary
6.4.1 create dictionary in list
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| alien_0 = {'color': 'green', 'points': 5}
alien_1 = {'color': 'yellow', 'points': 10}
alien_2 = {'color': 'red', 'points': 15}
aliens = [alien_0, alien_1, alien_2]
for alien in aliens:
print(alien)
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| {'color': 'green', 'points': 5}
{'color': 'yellow', 'points': 10}
{'color': 'red', 'points': 15}
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6.4.2 create list in dictionary
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| pizza = {
'crust': 'thick',
'toppings': ['mushrooms', 'extra cheese'],
}
print(f"You ordered a {pizza['crust']}-crust pizza "
"with the following toppings:")
for topping in pizza['toppings']:
print(topping)
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| You ordered a thick-crust pizza with the following toppings:
mushrooms
extra cheese
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6.4.3 create dictionary in dictionary
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| users = {
'einstein': {
'first': 'albert',
'last': 'einstein',
'location': 'princeton',
},
'curie': {
'first': 'marie',
'last': 'curie',
'location': 'paris',
},
}
for username, user_info in users.items():
print(f"\nUsername: {username}")
full_name = f"{user_info['first']}{user_info['last']}"
location = user_info['location']
print(f"\tFull name: {full_name.title()}")
print(f"\tLocation:{location.title()}")
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| Username: einstein
Full name: Alberteinstein
Location:Princeton
Username: curie
Full name: Mariecurie
Location:Paris
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