BC77 简单计算器

思路：

step1：分别计算加减乘除和错误输入；对应输出即可；

代码如下：

n = input()
# 加法：
if '+' in n:
    n = n.split('+')
    a = float(n[0])
    b = float(n[1])
    print('{:.4f}+{:.4f}={:.4f}'.format(a+0.00000001,b+0.00000001,a+b+0.00000001))

# 减法：
elif '-' in n:
    n = n.split('-')
    a = float(n[0])
    b = float(n[1])
    print('{:.4f}-{:.4f}={:.4f}'.format(a+0.00000001,b+0.00000001,a-b+0.00000001))

# 乘法：
elif '*' in n:
    n = n.split('*')
    a = float(n[0])
    b = float(n[1])
    print('{:.4f}*{:.4f}={:.4f}'.format(a+0.00000001,b+0.00000001,a*b+0.00000001))

# 除法：
elif '/' in n:
    n = n.split('/')
    a = float(n[0])
    b = float(n[1])
    if int(b) == 0:
        print('Wrong!Division by zero!')
    else:
        print('{:.4f}/{:.4f}={:.4f}'.format(a+0.00000001,b+0.00000001,a/b+0.00000001))

# 错误：
elif ('+' not in n) and ('-' not in n) and ('*' not in n) and ('/' not in n):
    print('Invalid operation!')