将用户输入添加到字典

Question

I've been attempting this for the last couple of hours and I just can't get the code right. I want to read in user input (eg 'red', 'blue', 'green', 'red') and spit out the colour and the count of that colour in a dictionary.

Here is my code - I know something is definitely not right with it especially in setting up the dictionary (it also has a while loop to continually ask for input until a blank is entered by the user)

INPUT: 'red', 'blue', 'green', 'red'

dict = {}
car_colours = input("Car: ")
frequency = 0
  while car_colours != '':
  dict['frequency'] = car_colours.count(car_colours)
  dict['colours'] = car_colours
  frequency = frequency + 1
  car_colours = input("Car: ")
print(dict)

I also assume I need a for loop to get the desired output below?

DESIRED OUTPUT

Cars that are red: 2
Cars that are blue: 1

I'm not actually even sure I even need this code in what I have above:

frequency = 0
frequency = frequency + 1

Thanks for any help!

Answer 1

There are few issues in your dictionary setup as you suspected.

'dict' is a keyword in python, I suggest avoiding that as variable name. Python dictionaries are not ordered usually. Instead of having frequency and color name separately, save the color name as key and count as value.

Here is the code with the above changes :

d = {}
count = 0
car_colours = raw_input("Car: ")
while car_colours != '':
    if d.has_key(car_colours):
        d[car_colours] = d[car_colours] + 1
    else:
        d[car_colours] = 1
    count = count + 1
    car_colours = raw_input("Car: ")

for k,v in d.iteritems():
    print 'Cars that are ' + k + ": " + str(v)

Here is sample test :

Answer 2

Why not use a more suitable data structure than dict ?

from collections import defaultdict

print "Enter car colours and ^C when done..."
try:
    car_count = defaultdict(int)
    while True:
        car_colour = raw_input("Car colour: ")
        car_count[car_colour] += 1
except KeyboardInterrupt:
    print
    print "Done with input, now the result"
    print

for c in car_count:
    print "Cars that are %s: %d" % (c, car_count[c])

Result will be:

$ python dd.py 
Enter car colours and ^C when done...
Car colour: red
Car colour: red
Car colour: green
Car colour: blue
Car colour: ^C
Done with input, now the result

Cars that are blue: 1
Cars that are green: 1
Cars that are red: 2
$

Note: Even when the int in car_count = defaultdict(int) is not formatted properly, it is a data type. The defaultdict extends dict such that each index that has not been accessed before automatically gets assigned the initial value of that type.