python 的keyerror问题

Question

我在敲《笨办法学python》这本书时遇到的问题，习题38。
我的代码如下：

# create a mapping of state to abbreviation
states = {
    'Oregon': 'OR',
    'Florida': 'FL',
    'California': 'CA',
    'New York': 'NY',
    'Michigan': 'MI'
}

#create a basic set of states and some cites in them
cities = {
    'CA': 'San Francisco',
    'MI': 'Detroit',
    'Fl': 'Jacksonville'
}

# add some more cities
cities['NY'] = 'New York'
cities['OR'] = 'Portland'

# print out some cities
print '-' * 10
print "NY State has: ", cities['NY']
print "OR State has: ", cities['OR']

# print some states
print '-' * 10
print "Michigan's abbreviation is: ", states['Michigan']
print "Florida's abbreviation is: ", states['Florida']

# do it by using the state then cities dict
print '-' * 10
print "Michigan has: ", cities[states['Michigan']]
print "Florida has: ", cities[states['Florida']]

# print evert state abbreviation
print '-' * 10
for state, abbrev in states.items():
    print "%s is abbreviated %s" % (state, abbrev)

# now do both at the same time
print '-' * 10
for state, abbrev in states.items():
    print "%s state is abbreviated %s has city %s" % (
        state, abbrev, cities[abbrev])

print '-' * 10
# safely get a abbreviation by states might not be there
state = states.get('Texas', None)

if not state:
    print "Sorry, no Texas."

# get a city with a default value
city = cities.get('TX', 'Does Not Exist')
print "The city for the state 'TX' is: %s " % city

命令行的信息如下：

----------
NY State has:  New York
OR State has:  Portland
----------
Michigan's abbreviation is:  MI
Florida's abbreviation is:  FL
----------
Michigan has:  Detroit
Florida has: 
Traceback (most recent call last):
  File "python_day1.py", line 34, in <module>
    print "Florida has: ", cities[states['Florida']]
KeyError: 'FL'

为什么会出现Keyerror呢？

Answer 1

请注意大小写

python#create a basic set of states and some cites in them
cities = {
    'CA': 'San Francisco',
    'MI': 'Detroit',
    'Fl': 'Jacksonville'  # l 是小写, 请改为 'FL'
}