-->字典用于以键：值对的形式存储数据值。
-->字典是一个有序的、可更改的、不允许重复的集合。
-->在字典中，每个元素都可以通过它们的键来访问，而不是通过索引。
-->如果字典不包含该键，则输出将为“KeyError”。
示例：
thisdict = {
"brand": "Ford",
"model": "Mustang",
"year": 1964
}
student = {"name":"raja", "class":5}
print(thisdict)
print(student)
输出：
{'brand': 'Ford', 'model': 'Mustang', 'year': 1964}
{'name': 'raja', 'class': 5}
练习：使用嵌套循环查找字符串中的字符
1.查找字符串中每个字母的频率
s = 'guruprasanna'
name = list(s)
j = 0
while j<len(name):
key = name[j]
count = 1
i = j+1
if key != '*':
while i<len(name):
if key == name[i]:
name[i] = '*'
count+=1
i+=1
print(key, count)
j+=1
输出：
g 1 u 2 r 2 p 1 a 3 s 1 n 2
*2。字母仅出现一次*
s = 'guruprasanna'
name = list(s)
j = 0
while j<len(name):
key = name[j]
count = 1
i = j+1
if key != '*':
while i<len(name):
if key == name[i]:
name[i] = '*'
count+=1
i+=1
if count == 1 and key!='*':
print(key, count)
j+=1
输出：
g 1 p 1 s 1
3。最常见的字母
s = 'guruprasanna'
name = list(s)
j = 0
while j<len(name):
key = name[j]
count = 1
i = j+1
if key != '*':
while i<len(name):
if key == name[i]:
name[i] = '*'
count+=1
i+=1
if count != 1 and key!='*':
print(key, count)
j+=1
输出：
u 2 r 2 a 3 n 2
4。第一个不重复的字母
s = 'guruprasanna'
name = list(s)
j = 0
while j<len(name):
key = name[j]
count = 1
i = j+1
if key != '*':
while i<len(name):
if key == name[i]:
name[i] = '*'
count+=1
i+=1
if count == 1 and key!='*':
print(key, count)
break
j+=1
输出：
g 1
5。第一个重复的字母
s = 'guruprasanna'
name = list(s)
j = 0
while j<len(name):
key = name[j]
count = 1
i = j+1
if key != '*':
while i<len(name):
if key == name[i]:
name[i] = '*'
count+=1
i+=1
if count != 1 and key!='*':
print(key, count)
break
j+=1
6。最后一个不重复的字母
last = ' '
last_count = 0
s = 'guruprasanna'
name = list(s)
j = 0
while j<len(name):
key = name[j]
count = 1
i = j+1
if key != '*':
while i<len(name):
if key == name[i]:
name[i] = '*'
count+=1
i+=1
if count == 1 and key!='*':
last = key
last_count = count
#print(key, count)
j+=1
print(last, last_count)
输出：
s 1
7。最后重复的字母
last = ' '
last_count = 0
s = 'guruprasanna'
name = list(s)
j = 0
while j<len(name):
key = name[j]
count = 1
i = j+1
if key != '*':
while i<len(name):
if key == name[i]:
name[i] = '*'
count+=1
i+=1
if count != 1 and key!='*':
last = key
last_count = count
#print(key, count)
j+=1
print(last, last_count)
输出：
n 2
8。最常见的字母
s = 'guruprasanna'
name = list(s)
j = 0
last = ' '
last_count = 0
while j<len(name):
key = name[j]
count = 1
i = j+1
if key != '*':
while i<len(name):
if key == name[i]:
name[i] = '*'
count+=1
i+=1
if count != 1 and key!='*':
if count>last_count:
last = key
last_count = count
j+=1
print(last, last_count)
9。元音出现频率 (a,e,i,o,u)
vowels = ['a','e','i','o','u']
last = ' '
last_count = 0
s = 'guruprasanna'
name = list(s)
j = 0
while j<len(name):
key = name[j]
if key in vowels:
count = 1
i = j+1
if key != '*':
while i<len(name):
if key == name[i]:
name[i] = '*'
count+=1
i+=1
if key!='*':
print(key, count)
j+=1
输出：
u 2 a 3
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