python课堂随记

11.15

连接符

name='mcl'
print('我叫',name)
print('我叫'+name)#连接符
age=18
print('我叫'+name+'年龄'+str(age))
#连接符需要数据类型相同

---

11.17随记

除法运算神奇

8/5     #1.6
8//5    #1
-8/5    #-1.6
-8//5   #-2

##次方表示---两个**

3的27次方

27的3次方

小结

程序的书写，包括代码缩进、注释、语句续行、关键字区分大小写等

内容

Python的数值类型数据和字符类型数据

Python的运算符包括算术运算符、比较运算符、逻辑运算符、赋值运算符等

Python不要求在使用变量之前声明其数据类型，但数据集类型决定了数的存储和操作的方式不同

3个函数：bool(),type(),len()

---

12.8随记

二分查找法

#ex0518.py
list1 = [1,42,3,-7,8,9,-10,5]
#二分查找要求查找的序列时有序的，假设是升序列表
list1.sort()
print(list1)
find=eval(input("请输入要查看的数据："))

low = 0
high = len(list1)-1
flag=False
while low <= high :
    mid = int((low + high) / 2)
    
    if list1[mid] == find :
        flag=True
        break
    #左半边
    elif list1[mid] > find :
        high = mid -1
    #右半边
    else :
        low = mid + 1
        
if flag==True:
    print("您查找的数据{},是第{}个元素".format(find,mid+1))
else:
    print("没有您要查找的数据")

统计单词出现的次数

#ex0517.py
sentence='Beautiful is better than ugly.Explicit is better than implicit.\
Simple is better than complex.Complex is better than complicated.'
#将文本中涉及标点用空格替换
for ch in ",.?!":
    sentence=sentence.replace(ch," ")
#利用字典统计词频
words=sentence.split()
map1={}
for word in words:
    if word in map1:
        map1[word]+=1
    else:
        map1[word]=1
#对统计结果排序
items=list(map1.items())
items.sort(key=lambda x:x[1],reverse=True)
#打印控制
for item in items:
    word,count=item
    print("{:<12}{:>5}".format(word,count))

---

12.13随记

6.1函数的定义和调用

def getarea(x,y):
    return x*y
print(getarea(3,2))
print(getarea("hello",2))

函数嵌套调用

def sum(n):
    def fact(a):
        t = 1
        for i in range(1,a+1):
            t*=i
        return t
    s = 0
    for i in range(1,n+1):
        s+=fact(i)
    return s
n = 5
print("{}以内的阶乘之和为{}".format(n,sum(n)))

6.2函数的参数和返回值

def getscore(pe,eng,math,phy,chem):
    return pe*0.5+eng*1+math*1.2+phy*1+chem*1
getscore(93,89,78,89,72) #按位置传递
getscore(pe=93,math=78,chem=72,eng=89,phy=89) #赋值传递 直接指定

参数数据类型：数值型 字符串型

组合数据类型：列表 元组 字典 集合 #传递地址

数值型

a = 10
def func(num):
    num += 1
    print("形参的地址 {}".format(id(num)))
    print("形参的值 {}".format(num))
    a = 1

func(a)
a,id(a)

组合数据类型

tup =(1,5,7,8,12,9)
ls = []
def getOdd(tup1,ls1):
    for i in tup1:
        if i%2:
            ls1.append(i)
    return ls1

getOdd(tup,ls)
print(ls)

#ex0608.py

def showmessage(name,age=18):
   "打印任何传入的字符串"
   print ("姓名: ",name)
   print ("年龄: ",age)
   return
 
#调用showmessage函数
showmessage(age=19,name="Kate" )
print ("------------------------")
showmessage(name="John")

#program0510.py
def showmessage(name,*p_info,**scores):
   print ("姓名: ",name)
   for e in p_info:
      print(e,end=" ")
   for item in scores.items():
      print(item,end=" ")
   print()   
   return
 
#调用showmessage函数
showmessage("Kate","male",18,"Dalian");
print("------------------------------")
showmessage("Kate","male",18,"Dalian",math=86,pe=92,eng=88)

def compare( arg1, arg2 ):
    result = arg1 >arg2
    return result    # 函数体内result值
btest= compare(10,9.99) # 调用sum函数
print ("函数的返回值: ",btest)

#ex0612.py
def findwords(sentence):
    "统计参数中含有字符e的单词，保存到列表中，并返回"
    result=[]
    words=sentence.split()
    for word in words:
        if word.find("e")!=-1:
            result.append(word)

    return result

ss="Return the lowest index in S where substring sub is found,"
print(findwords(ss))

---

12.15

闭包

print("okllll");
print("终于好了 姐要吐了")
def getarea(x,y):
    return x*y
print(getarea(3,2))
print(getarea("hello",2)

乱七八糟

#判断奇偶
def isodd(x):
    if type(x) != int:
        print("{}不是整数，退出程序!".format(x))
        return
    elif x%2==0:
        print("{}is even!".format(x))
        return False
    elif x%2==1:
        print("{}is odd!".format(x))
        return True

print(isodd(1))
print(isodd(2))
a=[1,2,3]
print(isodd(a))

练习

编写函数，计算某班级学生考试的平均分。

要求：

（1）班级共 10 人，计算平均分时可以根据全部人数或者实际参加考试人数计算。

（2）完成 avgScore()函数。

提示：

（1）定义函数 avgScore()时，参数 n 为默认参数，其默认值为 10。在调用函数 avgScore() 时，如果没有传入 n 的实参，则 n 取默认值；如果传入 n 的实参，则函数会使用传递给 n 的新值。

（2）函数 avgScore()用于计算考试成绩的平均分，接收列表类型的参数 scores。

---

12.20

python文件操作

主要考虑文件的读写

文件的打开和关闭

rb二进制读模式，wb二进制写模式

python文件读写的常用方法

read

f=open("test.txt","r")
str1=f.read(13)
print(str1)
str2=f.read()
print(str2)
f.close()

程序和文件需要放在同一个文件夹

#ex0903.py
f=open("test.txt","r")
flist=f.readlines()       # flist是包含文件内容的列表
print(flist)
for line in flist:
    print(line)           #使用print(line,end="")将不显示文件中的空行。
f.close()

#ex0904.py
f=open("test.txt","r")
str1=f.readline()

while str1!="":   #判断文件是否结束
    print(str1)
    str1=f.readline()
f.close()

write

fname = input("请输入追加数据的文件名:")
f1 = open(fname,"w+")
f1.write("向文件中写入字符串\n")
f1.write("继续写入")
f1.close()

跟指针相关，tell，seek

file = open("d:\\shiyan\\test.txt","r+")
str1 = file.read(6)
str1
file.tell()
file.readline()
file.tell()
file.readlines()
file.tell()
file.close()

file = open("d:\\shiyan\\test.txt","r+")
file.seek(6)
str1 = file.read(8)
str1
file.tell()
file.seek(6)
file.write("@@@@@@@")
file.seek(0)
file.readline()

#以'wb'方式打开二进制文件
fileb = open(r"d:\\shiyan\\mydata.dat","wb")
fileb.write(b"Hello Python")
n = 123
fileb.write(bytes(str(n),encoding='utf-8'))
fileb.write(b"\n3.14")
fileb.close()
#以'rb'方式打开二进制文件
file = open(r"d:\\shiyan\\mydata.dat","rb")
print(file.read())
file.close()
#以'r'方式打开二进制文件
filec = open(r"d:\\shiyan\\mydata.dat","r")
print(filec.read())
filec.close()

---

12.27随记

#ex0911.py
lst1 = ["read","write","tell","seek"]
dict1 = {"type1":"TextFile","type2":"BinaryFile"}
fileb = open(r"d:\\shiyan\\mydata.dat","wb")
#写入数据
import pickle
pickle.dump(lst1,fileb)
pickle.dump(dict1,fileb)
fileb.close()
#读取数据
fileb = open(r"d:\\shiyan\\mydata.dat","rb")
fileb.read()
fileb.seek(0)
x = pickle.load(fileb)
y = pickle.load(fileb)
x,y
fileb.close()

#ex0912.py
import shutil
shutil.copyfile("d:\\shiyan\\test.txt","d:\\shiyan\\testb.py")

#ex0913.py
import os,os.path
fname = input("请输入需要删除的文件名:")
if os.path.exists(fname):
    os.remove(fname)
else:
    print("{}文件不存在".format(fname))

#program0714.py 
import os,os.path,sys
fname=input("请输入需要更名的文件:")
gname=input("请输入更名后的文件名:")
if not os.path.exists(fname):
    print("{}文件不存在".format(fname))
    sys.exit(0)
elif os.path.exists(gname):
    print("{}文件已存在".format(gname))
    sys.exit(0)
else:
    os.rename(fname,gname)
print("rename success")

#ex0915.py
import os
os.getcwd()
os.listdir()
os.mkdir('myforder')
os.removedirs('yourforder\f1\f2')
os.makedirs('aforder\\ff1\\ff2')
import shutil
shutil.rmtree('yourforder')

#ex0916.py
# 向CSV文件中写入一维数据并读取
lst1 = ["name","age","school","address"]
filew= open('d:\\shiyan\\asheet.csv','w')
filew.write(",".join(lst1))
filew.close()

filer= open('d:\\shiyan\\asheet.csv','r')
line=filer.read()
print(line)
filer.close()

#ex0917.py
# 使用内置csv模块写入和读取二维数据

datas = [['Name', 'DEP', 'Eng','Math', 'Chinese'],
['Rose', '法学', 89, 78, 65],
['Mike', '历史', 56,'', 44],
['John', '数学', 45, 65, 67]
]

import csv
filename = 'd:\\shiyan\\bsheet.csv'
with open(filename, 'w',newline="") as f:
    writer = csv.writer(f)
    for row in datas:
        writer.writerow(row)   

ls=[]
with open(filename,'r') as f:
    reader = csv.reader(f)
    #print(reader)
    for row in reader:
        print(reader.line_num, row)    # 行号从1开始
        ls.append(row)
    print(ls)

#ex0919.py
filename=input("请输入要添加行号的文件名：")
filename2=input("请输入新生成的文件名：")
sourcefile=open(filename,'r',encoding="utf-8")
targetfile=open(filename2,'w',encoding="utf-8")
linenumber=""
for (num,value) in enumerate(sourcefile):
    if num<9:
        linenumber='0'+str(num+1)
    else:
        linenumber=str(num+1)
    str1=linenumber+"   "+value
    print(str1)
    targetfile.write(str1)
sourcefile.close()
targetfile.close()

#ex0920.py
from datetime import datetime
filename=input("请输入日志文件名：")
file=open(filename,'a')
print("请输入日志，exit结束")
s=input("log:")
while s.lower()!="exit":
    file.write("\n"+s)
    file.write("\n----------------------\n")
    file.flush()
    s=input("log:")
file.write("\n====="+str(datetime.now())+"=====\n")
file.close()

---

12.29 模块和库编程

from datetime import datetime
aday = datetime.now()
aday
print(aday)
dt1 = datetime(2021,9,10,13,59)
dt1
type(dt1)
print("当前时间是{}:{}:{}".format(dt1.hour,dt1.minute,dt1.second))

筛选key words

# program0617.py
'''
使用jieba库分解中文文本，并使用字典实现词频统计
'''
# encoding=utf-8
import jieba
# read need analyse file
article = open("shuihu70.txt",encoding='utf-8').read()
words = jieba.lcut(article)
#  count word freq
word_freq = {}
for word in words:
    if len(word)==1:
        continue
    else:
        word_freq[word]= word_freq.get(word,0)+1
#  sorted    
freq_word = []
for word, freq in word_freq.items():
    freq_word.append((word, freq))
freq_word.sort(key = lambda x:x[1], reverse=True)
max_number = eval(input("显示前多少位高频词？ "))
# display
for word, freq in freq_word[:max_number]:
    print(word, freq)

# program0618.py
'''
使用jieba库分解中文文本，并使用字典实现词频统计,统计结果中排除
部分单词，被排除单词保存在文件stopwords.txt中
'''
import jieba
stopwords = [line.strip() for line in open('stopwords.txt', 'r', \
                                           encoding='utf-8').readlines()] 
#  add extra stopword
stopwords.append('')
# read need analyse file
article = open("sanguo60.txt",encoding='utf-8').read()
words = jieba.cut(article, cut_all = False)
#  count word freq
word_freq = {}
for word in words:
    if (word in stopwords) or len(word)==1:
        continue
    if word in word_freq:
        word_freq[word] += 1
    else:
        word_freq[word] = 1
#  sorted    
freq_word = []
for word, freq in word_freq.items():
    freq_word.append((word, freq))
freq_word.sort(key = lambda x:x[1], reverse=True)
max_number = eval(input("需要前多少位高频词？ "))
# display
for word, freq in freq_word[:max_number]:
    print(word, freq)

# program0619.py
'''
使用jieba库分解中文文本，并使用字典实现词频统计,统计结果中排除
部分单词，被排除单词保存在文件stopwords.txt中，合并了部分同义词
'''
import jieba
stopwords=[line.strip() for line in open('stopwords.txt',\
                                         encoding='utf-8').readlines()] 
#  add extra stopword
stopwords.append('')
# read need analyse file
article = open("sanguo60.txt",encoding='utf-8').read()
words = jieba.lcut(article)
#  count word freq
word_freq = {}
for word in words:
    if (word in stopwords) or len(word)==1:
        continue
    elif word=='玄德' or word=='玄德曰':
        newword='刘备'
    elif word=='关公' or word=='云长':
        newword='关羽'
    elif word=='丞相':
        newword='曹操'
    elif word=='孔明' or word=='孔明曰':
        newword='诸葛亮'
    else:
         newword=word
         
    if newword in word_freq:
        word_freq[newword] += 1
    else:
        word_freq[newword] = 1
#  sorted    
freq_word = []
for word, freq in word_freq.items():
    freq_word.append((word, freq))
freq_word.sort(key = lambda x:x[1], reverse=True)
max_number = eval(input("需要前多少位高频词？ "))
# display
for word, freq in freq_word[:max_number]:
    print(word, freq)