Python期末复习
第二章 基本程序设计
eval('3') # 3
eval('3') + eval('4') # 7
eval('abc') #报错，abc没有定义
x , y = y ,x #x,y互换
eval('34') == eval('3' + '4')
integer = eval(input('Enter an integer:'))
q = integer // 1000
b = integer // 100 % 10
g = integer % 1000 % 100 // 10
s = integer % 1000 % 100 %10
print(s,g,b,q)
第三章 数字函数，字符串和对象
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符串和字符
ord('a') #返回字符的ascii码 97 chr(98) #返回ascii码的code字符 'b' -
对象和方法
n = 3 id(n) #2426581877040 type(n) #ints1 = 'HELLO' s1 = s1.lower() # 'hello' s1 s2 = 'hello' s2 = s1.upper() #'HELLO' s2 -
strip()：删除字符串两端的空格
s = '\t Welcome \n' s1 = s.strip() #'Welcome' s1 s = '\t \n\t123e\t12\nsa \t\n\t' s.strip() #'123e\t12\nsa' '''\t,\f,\r,\n都属于空格''' -
object.find(str(被查找字符）,beg = 0(开始索引),end(结束索引)).如果找到则返回object中第一次出现str的索引值，否则返回-1 。
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format() 函数 ‘.2f’ 四舍五入后保留小数点后2位小数
round(0.1532,2) # 0.15 format(0.125,'.2f') #'0.12' #数值类型默认右对齐，小数点也占一位 format(57.467657,'10.2f') #' 57.47' format(12345678.923,'10.2f') #'12345678.92' format(57.4,'10.2f') #' 57.40' format(57,'10.2f') #' 57.00' format(57,'.2f') #'57.00' #字符串默认左对齐 format('hello! Amber','20s') #'hello! Amber ' format('hello! Amber','<20s') #'hello! Amber ' format('hello! Amber','>20s') #' hello! Amber' format('hello! Amber!hello! Amber!','>20s') #'hello! Amber!hello! Amber!' # %也占一位 format(0.456789101112,'9.3%') #' 45.679%' format(0.456789101112,'<9.3%') #'45.679% ' -
object.split (str=’’,num = string.count(str))
str = 'Line1-abcdef \nLine2-abcdef \nLine3-abcdef' str.split() #['Line1-abcdef', 'Line2-abcdef', 'Line3-abcdef'] str.split(' ',1) #['Line1-abcdef', '\nLine2-abcdef \nLine3-abcdef'] s = 'apple,peach,banana,pear' s.split(',',2) #['apple', 'peach', 'banana,pear'] s = 'asda\t as\nsada saa\nasda' s.split('s') #['a', 'da\t a', '\n', 'ada ', 'aa\na', 'da'] s.split('\n') #['asda\t as', 'sada saa', 'asda']
第四章 选择
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布尔类型、值和表达式
- python用1代表True ;用0代表False
- True是python关键字；一个布尔字面量（对）；等同于1（错）
- Python将任何非零和非空值视为True,如果一个对象为0或者为空，那么被视为Flase
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生成随机数
- random.randint(a,b) 从范围[a,b]中返回一个随机整数，包括a和b
- random.random() 从范围(0,1)中返回一个随机**浮点数****
- randrange(a,b) 从范围[a,b)中返回一个随机整数，包括a但不包括b，与 random.randint(a,b - 1 )相同
- random.sample(object(eg.string,list),number) 多用于截取列表的指定长度的随机数，但不改变列表本身的顺序
random.randint(0,10) #8 random.random() #0.1632552069197507 random.randrange(0,10) #9 random.sample(range(1,100),3) #[25, 5, 82] random.sample(range(1,100),4) #[4, 53, 28, 79] -
if i > 0 : x = 1 y = 1可以使用任何宽度的空格，但一定要对齐
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条件表达式
if x > 0: y = 1 else: y = -1 y = 1 if x > 0 else -1 if number % 2 == 0: print(number,'is even.') else: print(number,'is odd.') print(number,'is even.' if number % 2 == 0 else 'is odd.')
第五章 循环
0 % 2 = 0 1 % 2 = 0
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举例
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乘法口诀表
#乘法口诀表 print(' Multiplication Table') print(' '* 2 ,end = ' ') for i in range(1,10): print(format(i,'4d'),end = ' ') print() print('-' * 4 * 12) for i in range(1,10): print(i,end = '| ') for j in range(1,10): print(format(i * j,'4d'),end = ' ') print()
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嵌套循环
for i in range(1,5): j = 0 while j < i: print(j,end = ' ') j += 1 # 0 0 1 0 1 2 0 1 2 3 i = 5 while i >= 1: num = 1 for j in range(1,i + 1): print(num,end = 'xxx') num *= 2 print() i -= 1 1xxx2xxx4xxx8xxx16xxx 1xxx2xxx4xxx8xxx 1xxx2xxx4xxx 1xxx2xxx 1xxx for i in range(1,9): print(' ' * 4 * (8 - i),end = ' ') for j in range(0,i): print(format(2 ** j ,'3d'),end = ' ') for j in range(0,i - 1): print(format(2 ** (i - j - 1),'3d'),end = ' ') print() -
找出最大公约数
#找出最大公约数 n1 = eval(input('Enter first integer:')) n2 = eval(input('Enter second integer:')) gcd = 1 k = 2 while k < min(n1,n2): if n1 % k == 0 and n2 % k == 0: gck = k k += 1 print(n1,'和',n2,'的最大公约数是',gck) #或者 n1,n2 = eval(input('Please enter two integer:')) for i in range(1,min(n1 + 1, n2 + 1)): if n1 % i == 0 and n2 % i == 0: a = i print(n1,'和',n2,'的最大公约数是',a) -
break 和 continue
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break帮助退出整个循环
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continue帮助退出或跳过当前的迭代
sum = 0 number = 0 while number < 20: number += 1 sum += number if sum >= 100: break print('The number is ',number,'\nThe sum is ',sum) #The number is 14 #The sum is 105 sum = 0 number = 0 while number < 20: number += 1 if number == 10 or number == 11: continue sum += number print('The sum is ',sum) # 10 与 11并没有加入 #The sum is 189#break and continue b = 1000 while 1: if b < 9: break b = b - 9 print('b is ',b) #b is 1 b = 1000 while 1: if b < 9: continue b = b - 9 print('b is ',b) #陷入死循环#break and continue for i in range(1,4): for j in range(1,4): if i * j > 2: break print( i * j) print(i) 1 2 1 2 2 3 for i in range(1,4): for j in range(1,4): if i * j > 2: continue print( i * j) print(i) 1 2 1 2 2 3#写一个程序，给出前50个素数，每行包含10个素数 print('The first 50 prime numbers are') print() count = 0 n = 2 while count < 50: for i in range(2,(n // 2 + 1)): if n % i == 0: break else: count += 1 print(format(n,'>5d'),end = ' ') if count % 10 == 0: print() n += 1
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第六章 对象和类
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一切事物都是对象，如类，函数等，因此对象并不只是一个类的实例
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init(self,…) self初始化：创建数据域
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self可以用其他变量代替，只是习惯上self
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不可变对象和可变对象
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举例
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class Count: def __init__(self,count = 0): self.count = count def main(): c = Count() times = 0 for i in range(100): increment(c,times) print('count is ',c.count) print('times is ',times) def increment(c,times): c = Count(times) times += 1 main() #count is 0 #times is 0
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隐藏数据域
- 缺陷:数据肯能会被篡改； 不利于维护
- 定义：__radius 通过2个下划线来定义私有数据域
- 私有数据域和方法仅能在类内部被访问，类外部不能被访问，除非提供一个方法返回它的值
- 类如果只是在程序内使用，而不是被其他程序使用，那么没有必要定义私有数据域
第七章 字符串、列表、集合和字典
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创建字符串
s = '' s1 = 'amber' s = str() s1 = str('amber') -
字符串的相关函数
len('\t') #1 len('\t 12') # -
索引操作符[]
index:[0,len(s) - 1]
s[-1] = s[-1 + len(s)]
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切片操作符
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s[start:end]:返回指定索引值从start到end -1的字符切片
s = 'welcome' s[1:4] #'elc' -
默认情况：start = 0，end 为最后一个
s[ :6] #'welcom' s[4: ] #'ome' -
如果 s[i:j]中的索引值i或j为负数，将它替换为len(s)+i或j
如果j > len(s),j默认为len(s)
如果i >= j，那么切片值为空字符s[1:-1] #'elcom' s[2:-3] #'lc'
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in 和 not in操作符
测试一个字符是否在另一个字符串中 返回布尔值
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迭代字符串
s = 'welcome' for ch in s : print(ch,end = " ") #w e l c o m e#将一个多位数反转 number = 123456 s = str(number) for i in range(len(s)): print(s[len(s) - i -1],end = ' ') # 6 5 4 3 2 1 # %% num = '' for i in range(len(s)): num = num + s[len(s)- i - 1] int(num) #654321 -
列表方法
list1 = [2,3,4,2,6,5,3,56] list1.append(19) #[2, 3, 4, 2, 6, 5, 3, 56, 19]list1.count(3) #2 list2 = [99,54] list1.extend(list2) list1 #[2, 3, 4, 2, 6, 5, 3, 56, 19, 99, 54] list1.insert(3,77) #index = 3,return None #[2, 3, 4, 77, 2, 6, 5, 3, 56, 19, 99, 54] list1.pop(3) #index = 3，return None #[2, 3, 4, 2, 6, 5, 3, 56, 19, 99, 54] list1.pop() #弹出最后一个字符,return最后一个字符 #54 [2, 3, 4, 2, 6, 5, 3, 56, 19, 99] list1.remove(56) #移除56，return None #[2, 3, 4, 2, 6, 5, 3, 19, 99] list1.reverse() #翻转列表 #[99, 19, 3, 5, 6, 2, 4, 3, 2] list1.sort() #排序 #[2, 2, 3, 3, 4, 5, 6, 19, 99] a,b = [1,2,3],[99,100] a.append(b) #[1, 2, 3, [99, 100]] a.append('a') a.append(['b']) #[1, 2, 3, [99, 100], 'a', ['b']] x的范围是1~10，将x中的每个元素值扩大3倍，并存入一个列表中 法1： list = [ i * 3 for i in range(1,11)] list #[3, 6, 9, 12, 15, 18, 21, 24, 27, 30] 法2： list2 = [] for i in range(1,11): list2.append(i * 3) list2 #[3, 6, 9, 12, 15, 18, 21, 24, 27, 30] -
列表解析
a = [x + y for x in 'ab' for y in '123'] a #['a1', 'a2', 'a3', 'b1', 'b2', 'b3'] -
复制列表 list2 = list1
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这条语句不是将list1中的内容赋给list2,而是将参考对象赋给list2，即他们指向同一个对象
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a = [1,2,3,4] b = a b #[1, 2, 3, 4] a[0] = -1 b #[-1, 2, 3, 4] b = a + [] #新建一个列表 等同于 b = a[:] a[0] = -2 a #[-2, 2, 3, 4] b #[-1, 2, 3, 4]
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举例
? 易混淆
def main(): list1 = add(1) print(list1) list2 = add(2) print(list2) list3 = add(3,[11,12,13,14]) print(list3) list4 = add(4) print(list4) main() [1] [1, 2] [11, 12, 13, 14, 3] [1, 2, 4] def add(x,lst = None): if lst == None: lst = [] if x not in lst: lst.append(x) return lst def main(): list1 = add(1) print(list1) list2 = add(2) print(list2) list3 = add(3,[11,12,13,14]) print(list3) list4 = add(4) print(list4) main() [1] [2] [11, 12, 13, 14, 3] [4]查找列表
#线性查找 --不需要排序 def linearSearch(lst,key): for i in range(len(lst)): if key == lst[i]: return i return -1 lst = [1,2,3,4,5,1,2,3,5] print(linearSearch(lst,5)) #4 print(linearSearch(lst,9)) #-1 #二分查找 --需要排序 def binarySearch(lst,key): low = 0 high = len(lst) - 1 while high >= low: mid = (high + low) // 2 if key <lst[mid]: high = mid - 1 elif key > lst[mid]: low = mid + 1 else: return mid return - low - 1 lst = [1,2,3,4,5,1,2,3,5] print(binarySearch(lst,5)) #4 print(binarySearch(lst,9)) #-10
第八章 多维列表集合和字典numpy
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打印列表
matrix = [[1,2,3],[4,5,6],[7,8,9]] 法1： for row in range(len(matrix)): for colum in range(len(matrix[row])): print(matrix[row][colum],end = ' ') print() 法2： for row in matrix: for value in row: print(value,end = ' ') print() 1 2 3 4 5 6 7 8 9 -
随机打乱顺序，random.shuffle(list)函数只能处理一维列表，不能处理多维列表
import random matrix = [[1,2,3],[4,5,6],[7,8,9]] for row in range(len(matrix)): for column in range(len(matrix[row])): i = random.randint(0,len(matrix) - 1) j = random.randint(0,len(matrix[row]) - 1) matrix[row][column],matrix[i][j] = matrix[i][j], matrix[row][column] print(matrix) #[[2, 1, 4], [3, 9, 6], [5, 7, 8]] #[[3, 1, 4], [8, 2, 9], [5, 7, 6]] -
排序 --sort()
points = [[4,2],[1,4],[2,5],[6,7],[1,2],[4,1]] points.sort() print(points) #[[1, 2], [1, 4], [2, 5], [4, 1], [4, 2], [6, 7]] -
易混淆
matrix = [] matrix.append(3 * [1]) matrix.append(3 * [1]) matrix.append(3 * [1]) print(matrix) matrix[0][0] = 2 print(matrix) [[1, 1, 1], [1, 1, 1], [1, 1, 1]] [[2, 1, 1], [1, 1, 1], [1, 1, 1]] matrix = [] matrix.append([3 * [1]]) matrix.append([3 * [1]]) matrix.append([3 * [1]]) print(matrix) matrix[0] = 3 print(matrix) [[[1, 1, 1]], [[1, 1, 1]], [[1, 1, 1]]] [3, [[1, 1, 1]], [[1, 1, 1]]] -
初始化列表 and 求和
#初始化列表 import random matrix = [] row = eval(input('Enter the row:')) column = eval(input('Enter the column:')) for i in range(row): matrix.append([]) for j in range(column): value = random.randint(0,99) matrix[i].append(value) print(matrix) #求和 def isSum(matrix): sum = 0 if matrix != None: for row in matrix: for value in row: sum = sum + value ''' for value in row: sum = sum + value 也可替换为： sum = sum + sum(row) sum()求列表的和 ''' return sum else: return False matrix = [[2, 1, 1], [1, 1, 1], [1, 1, 1]] print(isSum(matrix)) -
元组 和列表一样，但元素不可变，且元组的效率更高
元组一旦创建，就不能增删，替换元素，也不能改变顺序
注意 tuple([1,2,3]) == (1,2,3)；
tuple(list1.sort())会报错
t1 = () #() t2 = (1,2,3) #(1,2,3) t3 = tuple([2 * x for x in range(3)]) #(0,2,4) t4 = tuple('abac') #('a', 'b', 'a', 'c')tuple1 = ('a','b','c') ###注意 tuple([1,2,3]) == (1,2,3) tuple2 = tuple([1,2,3]) tuple3 = tuple1 + tuple2 tuple3 ('a','b','c',1,2,3)tuple1 = tuple([7,8,5,6,1,2,3,4]) list1 = list(tuple1) #[7, 8, 5, 6, 1, 2, 3, 4] list1.sort() #[1, 2, 3, 4, 5, 6, 7, 8] #tuple(list1.sort())会报错 -
集合
集合中没有重复的元素，也没有顺序，如果不考虑顺序的话，用集合比用列表的效率要高
集合无序，没有index方法
初始化 s1 = set() #set() s2 = {1,2,3} #{1, 2, 3} s3 = set([1,2,3]) #{1, 2, 3} s4 = set([x for x in range(5)]) #{0, 1, 2, 3, 4} s5 = set('abad') #{'a', 'b' , 'd'}相关操作 s1 = {1,2,3} s1.add(5) len(s1) #4 max(s1) #5 sum(s1) #11 3 in s1 #True s1.remove(2) #{1,3,5}子集与超集 如果s1中所有元素都在s2中，那么s1是s2的子集 s1.issubset(s2) 如果s2中所有元素都在s1中，那么s1是s2的超集 s1.issuperset(s2) s1 = {1,2,4} s2 = {1,4,5,2,6} s1.issubset(s2) #True s2.issuperset(s1) #True集合操作符 并集 s1 = {1,2,4} s2 = {1,3,5} s1.union(s2) #或s1 | s2 {1，2，3，4，5} 交集 s1.intersection(s2) #或s1 & s2 {1} 差集 s1.difference(s2) #或s1 - s2 {2,4} 对称差（异或） s1.symmetric_difference(s2) #s1 ^ s2 {2, 3, 4, 5} -
字典
存储键值对集合的容器对象。通过关键字实现快速获取、删除和更新值
字典中的关键字有点像列表中的索引，每个索引对应一个值，关键字不能相同，但其对应值可以相同 key:value
key只能是不可变对象，所以列表不能用来做key
a = {'1':'a','2':'b'} a = {} 添加、修改、获取值 students = {'201931990201':'a','201931990202':'b','201931990203':'3'} #{'201931990201': 'a', '201931990202': 'b', '201931990203': '3'} students['201931990209'] = 'amber' #{'201931990201': 'a', '201931990202': 'b', '201931990203': '3', '201931990209': 'amber'} students['201931990201'] = 'wenzhou' #{'201931990201': 'wenzhou', '201931990202': 'b', '201931990203': '3', '201931990209': 'amber'} print(students['201931990209']) #amber vegetables = [('celery',1.58),('brocoli',1.29),('lettuce',2.19)] dict = dict(vegetables) print(dict) {'celery': 1.58, 'brocoli': 1.29, 'lettuce': 2.19}删除与循环条目 a = {'abc':123,'cde':456} #{'abc': 123, 'cde': 456} del a ['cde'] print(a) #{'abc': 123} a = {'abc':123,'cde':456} for key in a: print(a[key]) 123 456字典方法 keys()返回关键字序列 tuple students = {'001':'amber1','002':'amber2','003':'amber3'} tuple(students.keys()) ('001', '002', '003') values()返回值序列 tuple tuple(students.values()) ('amber1', 'amber2', 'amber3') tuple(students.items()) (('001', 'amber1'), ('002', 'amber2'), ('003', 'amber3')) get(key) print(students.get('001')) amber1 pop(key)返回值，并删除 print(students.pop('001')) amber1 删除所有条目 students.clear() {}
numpy常用生成数组的函数 -->多维数组
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np.zero() np.empty() np.ones()
import numpy as np x= np.zeros(6) x array([0., 0., 0., 0., 0., 0.]) x = np.zeros((2,3)) array([[0., 0., 0.],[0., 0., 0.]]) np.empty((2,3)) array([[0., 0., 0.],[0., 0., 0.]]) np.ones((2,3)) array([[1., 1., 1.],[1., 1., 1.]]) np.ones([2,3]) array([[1., 1., 1.], [1., 1., 1.]]) -
利用arange(a,b,step)函数创建[a,b)之间以step为步长的一维数组
- 默认以0开始步长为1的整数序列
- arrange的参数可以是浮点数
array.shape 返回数组的维数
array.size 返回数组的元素个数
a = np.arange(6) array([0, 1, 2, 3, 4, 5]) a.shape (6,) a.size 6 np.arange(1,10,2) array([1, 3, 5, 7, 9]) np.arange(1,2,0.2) array([1. , 1.2, 1.4, 1.6, 1.8]) np.arange(1.2,3.1,0.3) array([1.2, 1.5, 1.8, 2.1, 2.4, 2.7, 3. ]) -
array.reshape(n,m,k)将数组array转换为n* m* k维矩阵
a = np.arange(12) a array([ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]) b = a.reshape(2,3,2) b array([[[ 0, 1], [ 2, 3], [ 4, 5]], [[ 6, 7], [ 8, 9], [10, 11]]]) b = a.reshape(2,3,-1) b array([[[ 0, 1], [ 2, 3], [ 4, 5]], [[ 6, 7], [ 8, 9], [10, 11]]])
第九章 文件操作
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文件分为二进制文件和文本文件
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打开文件
fileopen = open(filename,mode) 'r' 为读取打开一个文件 'w' 为写入打开一个文件，如果文件已存在，则销毁 'a' 打开一个文件从文件尾部追加数据 'rb'为读取二进制数据而打开文件 'wb'为写入二进制数据打开文件 #打开当前目录 fl = open('score.txt','r') #打开绝对目录下 f2 = open(r'C:\Users\LiuYixiu\Desktop\score.txtt','r') f2 = open('C:\\Users\\LiuYixiu\\Desktop\\score.txt','r') -
当我们对该目录下已存在的文件进行写操作时，已有的文件数据将会被新的文本覆盖或销毁
测试文件是否存在：import os.path
os.path.isfile(‘score.txt’)
存在返回True ,否则False
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读写文件 ！！！读取完要关闭
outfile = open('score.txt','w') outfile.write('Bill Clintor\n') outfile.write('George Bush\n') outfile.write('Barack Obama') outfile.close() -
从文件中读取所有数据：
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read()：读取剩下所有的数据，以字符串的形式返回
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readlines():读取剩下所有的数据，以字符串列表的形式返回，这里的字符串是原始数据
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注意：数据量太大以致于存储器无法存下，read(),readlines()方法都不可行，可以循环利用readline()解决
while line! = ‘’:
line = inflie.readline()
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open(‘xxx.txt’,‘a’)打开一个文件用于追加。如果该文件已存在，文件指针将会放在文件的结尾。也就是说，新的内容将会被写入到已有内容之后。如果该文件不存在，创建新文件进行写入。
def main(): inflie = open('score.txt','r') print('(1) Using read ():') print(inflie.read()) inflie.close() inflie = open('score.txt','r') print('\n(2) Using read (number):') s1 = inflie.read(4) print(s1) s2 = inflie.read(4) #repr()返回原始字符串 print(repr(s2)) inflie.close() inflie = open('score.txt','r') print('\n(3) Using readline ():') line1 = inflie.readline() line2 = inflie.readline() line3 = inflie.readline() line4 = inflie.readline() print(repr(line1)) print(repr(line2)) print(repr(line3)) print(repr(line4)) inflie.close() inflie = open('score.txt','r') print('\n(4) Using readlines ():') print(inflie.readlines()) inflie.close() main() ''' (1) Using read (): Bill Clintor George Bush Barack Obama (2) Using read (number): Bill ' Cli' (3) Using readline (): 'Bill Clintor\n' 'George Bush\n' 'Barack Obama' '' (4) Using readlines (): ['Bill Clintor\n', 'George Bush\n', 'Barack Obama'] '''#将一个源文件的数据复制到目标文件，并统计文件的行数和字符数 from os import path import os.path import sys def main(): f1 = input('Enter a source file:').strip() f2 = input('Enter a target file:').strip() if os.path.isfile(f2): print(f2 + 'already exists') sys.exit() infile = open(f1,'r') outfile = open(f2,'w') countLines = countChars = 0 for line in infile: countLines += 1 countChars += len(line) outfile.write(line) print(countLines,'lines and',countChars,'chars copied') infile.close() outfile.close() main()#在已存在的数据末尾添加数据 def main(): outfile = open('score.txt','a') outfile.write('\nhello amber\n') outfile.close() main()#读取数值数字，必须转换成字符类型 from random import randint def main(): outfile = open('score.txt','w') for i in range(10): outfile.write(str(randint(0,9))+' ') outfile.close() inflie = open('score.txt','r') s = inflie.read() numbers = [eval(x) for x in s.split()] for number in numbers: print(number,end = ' ') inflie.close() main() #8 1 1 9 3 6 2 6 4 5#统计文件中每个字符出现的次数，不区分大小写 def main(): filename = input('Enter a filename:') infile = open(filename,'r') counts = [0] * 26 for line in infile: countLetters(line.lower(),counts) for i in range(len(counts)): if counts[i] != 0: print(chr(ord('a') + i) + ' appears ' + str(counts[i]) + (' time ' if counts[i] == 1 else ' times')) infile.close() def countLetters(line,counts): for ch in line: if ch.isalpha(): counts[ord(ch) - ord('a')] += 1 main() ''' Enter a filename:score.txt a appears 6 times b appears 5 times c appears 12 times d appears 15 times f appears 11 times v appears 14 times ''' -
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从网站上获取数据
打开URL：使用函数urlopen(‘http://hao123.com’)
import urllib.request infile = urllib.request.urlopen('http://www.hao123.com') #read()读取字节数据类型的原始数据 #decode()将原始数据转换为字符串 print(infile.read().decode())import urllib.request def main(): url = input('Enter a URL for a file:') infile = urllib.request.urlopen(url) s = infile.read().decode() counts = countLetters(s.lower()) for i in range(len(counts)): if counts[i] != 0: print(chr(ord('a') + i) + ' appears ' + str(counts[i]) + (' time' if counts[i] == 1 else ' times')) def countLetters(s): counts = 26 * [] for ch in s: if ch.isalpha():#判断ch是否由英文字母组成 counts[ord(ch) - ord('a')] += 1 return counts main()
第十章 异常处理
def main():
try :
n1 ,n2 = eval(input('Enter two numbers,separated by a comma:'))
result = n1 / n2
print('Result is',result)
except ZeroDivisionError:
print('Division by zero!')
except SyntaxError:
print('A comma may be missing in the input')
except:
print('Something wrong in the input')
else:
print('No exceptions')
finally:
print('The finally clause is executed')
main()
'''
Enter two numbers,separated by a comma:3,4
Result is 0.75
No exceptions
The finally clause is executed
Enter two numbers,separated by a comma:2,0
Division by zero!
The finally clause is executed
Enter two numbers,separated by a comma:2 3
A comma may be missing in the input
The finally clause is executed
Enter two numbers,separated by a comma:a,v
Something wrong in the input
The finally clause is executed
'''
try :
statement1
statement2
except Exception1:
except Exception2:
except Exception3:
finally:
statement4
statement5
'''
若异常未被捕获，那么statement5不会执行，但会执行finally(statement4)
若异常类型是Exception3，那么statement4会执行,statement5也会执行
'''
try:
lst = [0] * 10
x = lst[9]
print('Done')
except IndexError:
print('Index out of bound')
else:
print('Nothing is wrong')
finally:
print('Finally we are here')
print('Coutinue')
'''
Done
Nothing is wrong
Finally we are here
Coutinue
'''
#抛出异常
def annonnegative():
a = eval(input('asdsa:'))
if a < 0:
raise RuntimeError('Negative radius')
else:
return a
try:
a1 = annonnegative()
print(a1)
except RuntimeError:
print('Invalid enter value.')
'''
asdsa:-1
Invalid enter value.
asdsa:2
2
'''
实验课
def isMinPrime(n):
i = 2
while True:
if n % i == 0:
print(i,end = ',')
n = n // i
else:
i = i + 1
if n == i:
print(i)
break
isMinPrime(120)
2，2，2，3，5
n = eval(input('Enter 1 ~ 15 :'))
for i in range(1,n + 1):
print(' ' * 4 * (n - i ),end = ' ')
for j in range(1 , i + 1):
print(format(i - j + 1,'3d'),end = ' ')
for j in range(1 , i):
print(format(j+1,'3d'),end = ' ')
print()
for j in range(10000,100001,10000):
e = 1
item = 1
for i in range(1 , j + 1):
item *= i
e += 1/item
print("i = %d 时， e = %.19f"%(j,e))
sum = 0
for i in range(1,50):
sum = ( 2 * i - 1)/(2 * i + 1) + sum
print(sum)
#判断一个数是否是素数
def isPrime(num):
tag = True
for i in range(2,(num // 2 + 1)):
if num % i != 0:
i = i + 1
else:
tag = False
return tag
#判断一个数是否是回文数
def isPalindrome(num):
tag = True
s = str(num)
if s[::-1 ] == s[::]:
return True
else:
return False
#输出前100个回文素数
def print1():
count = 0
k = 2
while count < 100:
if isPalindrome(k) and isPrime(k):
count = count + 1
print(format(k,'6d'),end = ' ')
if count % 10 == 0:
print()
k = k + 1
print1()
def finder(str1,str2):
if str2 in str1:
return True
else:
return False
print(finder('abc','a'))
输入1到100之间的整数，统计出现的次数
a = input('Enter integers between 1 and 100:').split()
counts = []
b = list(set( eval(x) for x in a))
b.sort()
for i in range(len(b)):
item = a.count(str(b[i]))
print(b[i],'occurs ', item ,' time' if item == 1 else 'times')
matrix = []
def sumMajorDiagonal(matrix):
sum = 0
for i in range(len(matrix)):
sum = sum + float(matrix[i][i])
print('Sum of the elements in the major diagonal is',sum)
for i in range(4):
a = input('Enter a 4-by-4 matrix row for row '+str(i)+':').split()
matrix.append(a)
sumMajorDiagonal(matrix)
def main():
matrix1 = []
matrix2 = []
s = input("Enter a 3-by-3 matrix1: ")
items = s.split() # Extracts items from the string
for i in range(3):
list = [eval(items[j]) for j in range(3 * i, 3 * i + 3)] # Convert items to numbers
matrix1.append(list)
s = input("Enter a 3-by-3 matrix2: ")
items = s.split() # Extracts items from the string
for i in range(3):
list = [eval(items[j]) for j in range(3 * i, 3 * i + 3)] # Convert items to numbers
matrix2.append(list)
matrix3 = multiplyMatrix(matrix1, matrix2)
printResult(matrix1, matrix2, matrix3, "*")
def multiplyMatrix(m1, m2):
list = len(m2[0]) * [0]
result = []
for i in range(len(m1)):
result.append([x for x in list])
for i in range(len(result)):
for j in range(len(result[0])):
for k in range(len(m2)):
result[i][j] += m1[i][k] * m2[k][j]
return result
# Print result
def printResult(m1, m2, m3, op):
for i in range(len(m1)):
for j in range(len(m1[0])):
print(" " + str(m1[i][j]), end = "")
if i == len(m1) // 2:
print( " " + op + " ", end = "")
else:
print( " ", end = "")
for j in range(len(m2[0])):
print(" " + str(m2[i][j]), end = "")
if i == len(m1) // 2:
print(" = ", end = "")
else:
print(" ", end = "")
for j in range(len(m3[0])):
print(" " + str(m3[i][j]), end = "")
print()
main()
'''
Enter a 3-by-3 matrix1: 1 2 3 4 5 6 7 8 9
Enter a 3-by-3 matrix2: 0 2 4 1 4.5 2.2 1.1 4.3 5.2
1 2 3 0 2 4 5.300000000000001 23.9 24.0
4 5 6 * 1 4.5 2.2 = 11.600000000000001 56.3 58.2
7 8 9 1.1 4.3 5.2 17.9 88.69999999999999 92.4
'''
#13.1
filename = input('Enter a filename:')
content = input('Enter the string to be removed:')
infile = open(filename,'r')
for line in infile:
line = line.replace(content,'')
print(line)
infile.close()
'''
Enter a filename:score.txt
Enter the string to be removed:okk
Amber!
good moring!
haha!1
abchsfndvjmfkvmfjvfvjfjivjvjnj!
'''
'''
Enter a filename:score.txt
Enter the string to be removed:1
Amber!
good moring!
haha!okkokk
abchsfndvjmfkvmokkfjvfvjokkfjivjvjnjokk!
'''
#13.2
def main():
f1 = input("Enter a filename: ").strip()
infile = open(f1, "r")
s = infile.read()
print(str(len(s)) + " characters")
print(str(len(s.split())) + " words")
print(str(len(s.split('\n'))) + " lines")
infile.close()
main()
'''
Enter a filename: score.txt
69 characters
6 words
7 lines
'''