为什么我的python dict变得无序？

参见英文答案 > Why is python ordering my dictionary like so? ????????????????????????????????????3个
>???????????? Dictionaries: How to keep keys/values in same order as declared?????????????????????????????????????12个
我用这个来制作一个多年来以某个字母开头的名字百分比图.当绘制(和打印)我的词典(letter_d)时,键是无序的,而不是像它们被添加到词典中一样顺序.有没有办法解决这个问题,我相信我会按顺序将它们添加到dict中.如果没有,我可以创建一个方法连接我的散点图的点,以模拟正确的线图？

import csv
import matplotlib.pyplot as plt 

start = 1880
stop = 1890
x = []
years = range(start,stop +1)
print years
letter_d = {}
year_d = {}
alphabet = ['Z']#,'C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z']

for i in alphabet:
    letter_d[i] = 0

for year in years:
    filename = 'yob' + str(year) + '.txt'
    z = open(filename)      
    year_d[int(year)] = 0
    letter_d[i] = year_d
    c = 0
    d = 0
    for line in z:
        y = line.strip().split(',')
        y.remove(y[1])
        c += int(y[1])
        if i in y[0]:
            d += int(y[1])
        year_d[year] = float(d)/float(c)            
        #x.append(y)
#print year_d
print year_d.keys()
plt.plot(year_d.keys(),year_d.values())
plt.show()

year_values = []

for year in years:
    # ...
    year_values.append(float(d)/float(c))

plt.plot(years,year_values)