Python第六章（北理国家精品课 嵩天等）

一

1.集合类型定义及其操作：

集合用{}表示，元素用逗号分隔，无序，唯一

集合操作符：

|：并

-：减

&：交

^ ：补

<= <：判断子集关系

>= >：判断包含关系

|=：

-=：

&=：

^=：

集合处理方法：

S.add(x)  字面意思

S.discard(x) 移除S中元素x，若不在，不报错

S.remove(x) 移除S中元素x，若不在，产生KeyError异常

S.clear(x) 移除S中所有元素

S.pop(x) 随机返回S的一个元素，更新S，若S为空产生KeyError异常

S.copy()

len(S)

x in S

x not in S

set(x)

集合类型应用场景：

包含关系比较

元素去重

2.序列类型及其操作：

定义：一维元素向量，元素类型可以不同

比如字符串

序列操作符：in, not in,s+t,s*n,s[i],s[i:j:k]

函数：len(s),min(s),max(s),s.index(x)或s.index(x,i,j),返回序列s从i开始到j位置中第一次出现x的位置，s.count(x)，返回s中出现x的总次数

元组类型及其操作：一旦创建不能被更改，tuple()

列表类型及其操作：可以随意修改，使用[]或list()创建

ls[i] = x

ls[i:j:k] = lt

del s[i],del ls[i:j:k]删除

ls += lt

ls *= n

ls.append(x) 在列表ls最后增加一个元素x

ls.clear()

ls.copy()

ls.insert(i,x)

ls.pop(i) 取出并删除

ls.remove(x) 删除第一个x

ls.reverse() 将ls中的元素反转

3.序列类型应用场景：

item遍历

4.sorted排序

二

基本统计值实例

#CalStatisticsV1.py
def getNum():
    nums = []
    iNumStr = input("请输入数字(回车退出)：")
    while iNumStr !="":
        nums.append(eval(iNumStr))
        iNumStr = input("请输入数字(回车退出)：")
    return nums

def mean(numbers):
    s = 0.0
    for num in numbers:
        s = s+num
    return s / len(numbers)

def dev(numbers,mean):
    sdev = 0.0
    for num in numbers:
        sdev = sdev + (num-mean)**2
    return pow(sdev / (len(numbers)-1),0.5)

def median(numbers):
    sorted(numbers)
    size = len(numbers)
    if size % 2 == 0:
        med = (numbers[size//2-1]+numbers[size//2])/2
    else:
        med = numbers[size//2]
    return med

n = getNum()
m = mean(n)
print("平均值:{},方差:{:.2},中位数:{}".format(m,dev(n,m),median(n)))
    

三、字典类型

映射是键和值的对应

采用{}和dict()创建，键值对用冒号:表示

d = {"C":"B","M":"H","F":"B"}
>>> d
{'C': 'B', 'M': 'H', 'F': 'B'}
>>> d["C"]

del d[k] 删除字典d中键k对应的数据值

k in d 判断键k是否在字典中

d.keys() 返回字典d中所有的键信息

d.values() 返回字典d中所有的值信息

d.items() 返回字典d中所有的键值对信息

>>> d = {"中国":"北京","美国":"华盛顿","法国":"巴黎"}
>>> "中国" in d
True
>>> d.keys()
dict_keys(['中国', '美国', '法国'])
>>> d.values()
dict_values(['北京', '华盛顿', '巴黎'])

d.get(k,<default>) 键k存在，则返回相应的值，不在，则返回<default>值

d.pop(k,<default>) 键k存在，则取出相应的值，不在，则返回<default>值

d.popitem() 随机从字典d中取出一个键值对，以元组形式返回

d.clear() 删除所有键值对

len(d) 返回字典d中元素的个数

>>> d.get("中国","伊斯兰堡")
'北京'
>>> d.get("日本","伊斯兰堡")
'伊斯兰堡'
>>> d.popitem()
('法国', '巴黎')
定义空字典 ：d = {}
向d增加两个键值对元素：d["a"] = 1;d["b"] = 2

字典类型应用场景：

四、jieba库

Microsoft Windows [版本 10.0.17134.648]
(c)  Microsoft Corporation。保留所有权利。

C:\Users\ASUS>pip install jieba
Collecting jieba
  Downloading https://files.pythonhosted.org/packages/71/46/c6f9179f73b818d5827202ad1c4a94e371a29473b7f043b736b4dab6b8cd/jieba-0.39.zip (7.3MB)
    % |████████▌                       | .9MB 19kB/s eta ::32Exception:
Traceback (most recent call last):
  File "c:\users\asus\appdata\local\programs\python\python37-32\lib\site-packages\pip\_vendor\urllib3\response.py", line , in _error_catcher
    yield
  File "c:\users\asus\appdata\local\programs\python\python37-32\lib\site-packages\pip\_vendor\urllib3\response.py", line , in read
    data = self._fp.read(amt)
  File "c:\users\asus\appdata\local\programs\python\python37-32\lib\site-packages\pip\_vendor\cachecontrol\filewrapper.py", line , in read
    data = self.__fp.read(amt)
  File "c:\users\asus\appdata\local\programs\python\python37-32\lib\http\client.py", line , in read
    n = self.readinto(b)
  File "c:\users\asus\appdata\local\programs\python\python37-32\lib\http\client.py", line , in readinto
    n = self.fp.readinto(b)
  File "c:\users\asus\appdata\local\programs\python\python37-32\lib\socket.py", line , in readinto
    return self._sock.recv_into(b)
  File "c:\users\asus\appdata\local\programs\python\python37-32\lib\ssl.py", line , in recv_into
    return self.read(nbytes, buffer)
  File "c:\users\asus\appdata\local\programs\python\python37-32\lib\ssl.py", line , in read
    return self._sslobj.read(len, buffer)
socket.timeout: The read operation timed out

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "c:\users\asus\appdata\local\programs\python\python37-32\lib\site-packages\pip\_internal\cli\base_command.py", line , in main
    status = self.run(options, args)
  File "c:\users\asus\appdata\local\programs\python\python37-32\lib\site-packages\pip\_internal\commands\install.py", line , in run
    resolver.resolve(requirement_set)
  File "c:\users\asus\appdata\local\programs\python\python37-32\lib\site-packages\pip\_internal\resolve.py", line , in resolve
    self._resolve_one(requirement_set, req)
  File "c:\users\asus\appdata\local\programs\python\python37-32\lib\site-packages\pip\_internal\resolve.py", line , in _resolve_one
    abstract_dist = self._get_abstract_dist_for(req_to_install)
  File "c:\users\asus\appdata\local\programs\python\python37-32\lib\site-packages\pip\_internal\resolve.py", line , in _get_abstract_dist_for
    self.require_hashes
  File "c:\users\asus\appdata\local\programs\python\python37-32\lib\site-packages\pip\_internal\operations\prepare.py", line , in prepare_linked_requirement
    progress_bar=self.progress_bar
  File "c:\users\asus\appdata\local\programs\python\python37-32\lib\site-packages\pip\_internal\download.py", line , in unpack_url
    progress_bar=progress_bar
  File "c:\users\asus\appdata\local\programs\python\python37-32\lib\site-packages\pip\_internal\download.py", line , in unpack_http_url
    progress_bar)
  File "c:\users\asus\appdata\local\programs\python\python37-32\lib\site-packages\pip\_internal\download.py", line , in _download_http_url
    _download_url(resp, link, content_file, hashes, progress_bar)
  File "c:\users\asus\appdata\local\programs\python\python37-32\lib\site-packages\pip\_internal\download.py", line , in _download_url
    hashes.check_against_chunks(downloaded_chunks)
  File "c:\users\asus\appdata\local\programs\python\python37-32\lib\site-packages\pip\_internal\utils\hashes.py", line , in check_against_chunks
    for chunk in chunks:
  File "c:\users\asus\appdata\local\programs\python\python37-32\lib\site-packages\pip\_internal\download.py", line , in written_chunks
    for chunk in chunks:
  File "c:\users\asus\appdata\local\programs\python\python37-32\lib\site-packages\pip\_internal\utils\ui.py", line , in iter
    for x in it:
  File "c:\users\asus\appdata\local\programs\python\python37-32\lib\site-packages\pip\_internal\download.py", line , in resp_read
    decode_content=False):
  File "c:\users\asus\appdata\local\programs\python\python37-32\lib\site-packages\pip\_vendor\urllib3\response.py", line , in stream
    data = self.read(amt=amt, decode_content=decode_content)
  File "c:\users\asus\appdata\local\programs\python\python37-32\lib\site-packages\pip\_vendor\urllib3\response.py", line , in read
    raise IncompleteRead(self._fp_bytes_read, self.length_remaining)
  File "c:\users\asus\appdata\local\programs\python\python37-32\lib\contextlib.py", line , in __exit__
    self.gen.throw(type, value, traceback)
  File "c:\users\asus\appdata\local\programs\python\python37-32\lib\site-packages\pip\_vendor\urllib3\response.py", line , in _error_catcher
    raise ReadTimeoutError(self._pool, None, 'Read timed out.')
pip._vendor.urllib3.exceptions.ReadTimeoutError: HTTPSConnectionPool(host='files.pythonhosted.org', port=): Read timed out.
You are using pip version 18.1, however version 19.0. is available.
You should consider upgrading via the 'python -m pip install --upgrade pip' command.

C:\Users\ASUS>python -m pip install --upgrade pip
Collecting pip
  Downloading https://files.pythonhosted.org/packages/d8/f3/413bab4ff08e1fc4828dfc59996d721917df8e8583ea85385d51125dceff/pip-19.0.3-py2.py3-none-any.whl (1.4MB)
    % |████████████████████████████████| .4MB 20kB/s
Installing collected packages: pip
  Found existing installation: pip 18.1
    Uninstalling pip-18.1:
      Successfully uninstalled pip-18.1
Successfully installed pip-19.0.

C:\Users\ASUS>pip install jieba
Collecting jieba
  Downloading https://files.pythonhosted.org/packages/71/46/c6f9179f73b818d5827202ad1c4a94e371a29473b7f043b736b4dab6b8cd/jieba-0.39.zip (7.3MB)
    % |████████████████████████████████| .3MB 445kB/s
Installing collected packages: jieba
  Running setup.py install for jieba ... done
Successfully installed jieba-0.39

C:\Users\ASUS>

精确模式：把文本精确地切分开，不存在冗余单词

全模式：有冗余

搜索引擎模式：在精确模式基础上，对长词再次切分

函数：

jieba.lcut(s) ，精确模式，返回一个列表类型的分词结果

jieba.lcut(s,cut_all=True) ，全模式，返回一个列表类型的分词结果,存在冗余

jieba.lcut_for_search(s) ，搜索引擎模式，返回一个列表类型的分词结果,存在冗余

jieba.add_word(w) 向分词词典增加新词w

>>> import jieba
>>> jieba.lcut("中国是一个伟大的国家")
Building prefix dict from the default dictionary ...
Dumping model to file cache C:\Users\ASUS\AppData\Local\Temp\jieba.cache
Loading model cost 1.139 seconds.
Prefix dict has been built succesfully.
['中国', '是', '一个', '伟大', '的', '国家']
>>> jieba.lcut("中国是一个伟大的国家")
['中国', '是', '一个', '伟大', '的', '国家']
>>> jieba.lcut("中国是一个伟大的国家",cut_all=True)
['中国', '国是', '一个', '伟大', '的', '国家']
>>> jieba.lcut_for_search("中华人民共和国是伟大的")
['中华', '华人', '人民', '共和', '共和国', '中华人民共和国', '是', '伟大', '的']

五、“文本词频统计”实例

#CalHamletV1.py
def getText():
    txt = open("hamlet.txt","r").read() #读取文本
    txt = txt.lower()
    for ch in '~!@#$%^&*()_+{}:"<>?[];,./-=':
        txt = txt.replace(ch," ")
    return txt

hamletTxt = getText()
words = hamletTxt.split()
counts = {}
for word in words:
    counts[word] = counts.get(word,0)+1   #统计词频
items = list(counts.items())
items.sort(key=lambda x:x[1],reverse=True) #降序排列
for i in range(10):
    word,count = items[i]
    print("{0:<10}{1:>5}".format(word,count))

#CalThreeKingdomsV1.py
import jieba
txt = open("threekingdoms.txt","r",encoding="utf-8").read()
words = jieba.lcut(txt)
counts = {}
for word in words:
    if len(word)==1:
        continue
    else:
        counts[word] = counts.get(word,0)+1
items = list(counts.items())
items.sort(key=lambda x:x[1],reverse=True)
for i in range(15):
    word,count = items[i]
    print("{0:<10}{1:>5}".format(word,count))
运行遇到问题，直接评论即可

#CalThreeKingdomsV2.py
import jieba
excludes= {"将军","却说","荆州","二人","不可","不能","如此","商议","如何","军士"}
txt = open("threekingdoms.txt","r",encoding="utf-8").read()
words = jieba.lcut(txt)
counts = {}
for word in words:
    if len(word)==1:
        continue
    elif word=="诸葛亮" or word=="孔明曰":
        rword = "孔明"
    elif word=="关公" or word=="云长":
        rword = "关羽"
    elif word=="玄德" or word=="玄德曰":
        rword = "刘备"
    elif word=="孟德" or word=="丞相曰" or word=="丞相" or word=="主公":
        rword = "曹操"
    else:
        rword = word
    counts[rword] = counts.get(rword,0)+1
for word in excludes:
    del counts[word]
items = list(counts.items())
items.sort(key=lambda x:x[1],reverse=True)
for i in range(15):
    word,count = items[i]
    print("{0:<10}{1:>5}".format(word,count))