python学习字符，列表，print

2019.3.23

1、输入一个整数，求输入的数的平方；需要注意的是，input得到的是一个字符串，所以要将得到的字符串转换成int型，才能进行计算。

#input an integer number:

a = input("please input an integer number：")
a = int(a)
print(a**2)

2、 输入三个整数，并输出最小值，得到的三个数依旧要先进行类型转换，之后再用min（）函数得到最小值。

#input three integer number:

list = []
for i in range(3):
    st = input("please input an integer number ：")
    st = int(st)
    list+=[st]
print(min(list))

3、输入五个整数，得到列表[0,1,2,3,4]，然后选用两种切片方法输出[1,3]两个值

#input five integer number:

list = []
for i in range(5):
    st = input("please input an integer number ：")
    st = int(st)
    list+=[st]
print(list)
print(list[1::2])   #withdraw a list with separate one number methord one
print("the number one is {} ".format(list[1]))#methord two
print("the number three is {}".format(list[3]))
print(list[3:0:-2])#methord three

4、创建一个字典，实现初始化字典{'a':1,'b':2}，设置其key为'c'的对应值为3

#construct an dictionary
#method one

dict1 = {'a':1,'b':2,'c':3}
print("the result of first method is {}".format(dict1.get('c')))

#method two 

dict2 = dict()
dict2['a'] = '1'
dict2['b'] = '2'
dict2['c'] = '3'
print("the result of second method is {}".format(dict2.get('c')))

#method three

a = ["a","b","c"]
b = ['1','2','3']
d = {}
for i in range(len(a)):
    d[a[i]] = b[i] 
print(d)
print("the result of third method is {}".format(d.get('c')))

#method fourth

dic = dict((['a',1],['b',2]))
dic1 = dict((['c',3],['d',4]))
dic.update(dic1)
print("the result of fourth method is {}".format(dic.get('c')))

5、输入某科目前10个人的成绩，求其总分和平均分

#input ten student‘s grade score
list = []
sum = 0
print("please input ten student's score :") 
for i in range(10):
    st = input()
    st = int(st)
    sum+=st
    list+=[st]
a = len(list)
average = sum /a
print(type(average))
print("the total score is {}".format(sum))
print("the average score is {}".format(average))

 6、print()函数里面的end = '' 表示的含义：end = '' 的作用是传递一个空字符串，print默认是打印一行，结尾加上换行。end = ''的意思是末尾不换行，加空格。

# choice question

for i in range(3):
    for j in range(i,3):
        print('+',end='') #end = '' 的作用是传递一个空字符串，print默认是打印一行，结尾加上换行。end = ''的意思是末尾不换行，加空格。
    print()

7、根据得到的分数进行评价，每个阶段的分数得到的反馈结果不一样。

# grade according to the score

x = input("please input your total score:")
x = float(x)
if x >= 90:
    print("your grade is excellent")
elif x >= 80:
    print("your grade is well")
elif x >= 70:
    print("your grade is good")
elif x >= 60:
    print("your grade is common")
else:
    print("you can do it!! cheer up!")

8、for 循环的应用和 continue、break之间的区别

#the different between 'continue' and 'break'
for i in [1,2,3,4,5,6]:
    print(i)
    if i == 2:
        continue
    print(i,"square is:",i**2)
    if i == 4:
        break
else:
    print("loop end!")

9、计算两个数之间的素数

# caculate all prime number between two numbers the user have input

x = (int(input('please input start number:')),int(input('please input end number:')))
           #explain:input two integer and put them in tuple
x1 = min(x)
x2 = max(x)
list = []
for n in range(x1,x2+1):
    for i in range(2,n-1):
        if n % i == 0:
            break
    else:
        print(n,"is prime number.")
#explain:list+=[n]
#explain:print(list,"is prime number.") this is another way to show the result

10、for和rangea()函数的使用

# for and range()

print(' the first loop output:')
for i in range(4):
    print(i)

print(' the second loop output:')
for i in range(0,7,2):
    print(i)

11、for遍历字典的例子

# for traverse dictionary

adct = {'apple':15,'banana':23,'pear':12}
for key,value,in adct.items():
    print(key,':',value)
for key in adct.keys():
    print(key)
for value in adct.values():
    print(value)

12、输入20个数，将正数和负数分别放在两个列表并且输出

# separate positive number and non-positive number

list1 = []
list2 = []
print("please input twenty positive number or non-positive number:")
for i in range(20):
    a = input()
    a = int(a)

    if a > 0:
        list1+=[a]
    elif a<0:
        list2+=[a]
    else:
        continue
print("the positive number is:",list1)
print("the non-positive number is:",list2)