python-基础语法

一.  基础

1.  else子句

  当循环正常执行，则不执行，若非正常退出（break），则不执行else子句

for i in range(0,10):
    if i & 1:
        continue
    print(i)
else:
    print("执行") # 执行

for i in range(0,10):
    if i & 1:
        break
    print(i)
else:
    print("不执行")

2.打印边长为n的正方形（*）

n = 5
e = - (n // 2)
for i in range(e,n+e):
    if i == e or i == n+e-1:
        print(n * '*')
    else:
        print("*" + " " * (n - 2) + "*")

3.打印九九乘法表

# 九九乘法表
n = 9
for i in range(1,n+1):
    for j in range(1,i+1):
        print(str(j) + "*" + str(i)+ "=" + str(i*j),end=' ')
    print()

4.输入若干个数，输出最大值

max = int(input("输入第一个数："))
while True:
    a = input("输入另一个数：")
    if a:
        n = int(a)
        if n > max:
            max = n
        print("max:" ,max)
    else:
        break

5.输入n个数的算数平均值

sum = 0
n = 0
while True:
    i = int(input("请输入一个数字："))
    n = n + 1
    sum = sum + i
    avg = sum / n
    print(str(n) + "个数的算数平均数是：" + str(avg))

6.打印菱形

n = 7
e = -n // 2
for i in range(e, n + e + 1):  # -3 -2 -1 0 1 2 3
    if i < 0:
        prespace = -i
    else:
        prespace = i
    print(' ' * prespace + '*' * (n - prespace * 2))

 7.打印倒99乘法表

# 倒九九乘法表
for i in range(1,10):
    s = ""
    for j in range(i,10):
        s = s + "{}*{}={} ".format(i,j,i*j)
    print("{:>55}".format(s))

8.杨辉三角

triangle = [[1],[1,1]]
for i in range(2,10):
    start = 1
    next = []
    next.append(start)
    for j in range(i-1):
        temp = triangle[i-1][j] + triangle[i-1][j+1]
        next.append(temp)
    else:
        next.append(1)
    triangle.append(next)
for i in triangle:
    print(i)

9.矩阵转置

matxix = [[1,2,3],[4,5,6],[7,8,9]]
for i,row in enumerate(matxix):
    for j,col in enumerate(row):
        if j > i:
            matxix[i][j],matxix[j][i] = matxix[j][i],matxix[i][j]
print(matxix)

10.随机生成10个数字，统计相同的数字有哪些，分别是什么，不同的数字有哪些？

import random

num = []
for _ in range(20):
    num.append(random.randrange(21))
print(num)

length = len(num)
samenums = []
diffnums = []
state = [0] * length

for i in range(length):
    flag = False
    if state[i] == 1:
        continue
    for j in range(i+1,length):
        if state[j] == 1:
            continue
        if num[i] == num[j]:
            flag = True
            state[j] = 1
    if flag:
        samenums.append(num[i])
        state[i] = 1
    else:
        diffnums.append(num[i])
print(samenums)
print(diffnums)