Python100Days-day3分支结构

Python语句的特点
Python没有花括号来构造代码块
Python通过缩进来设置层次结构
如果在条件语句中同时执行多条语句，保持相同缩进即可
即连续代码又保持相同缩进，它们就是同一代码块，是一个执行整体
Flat is better than nested.尽量减少嵌套
分支结构语句
if … :
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elif … :
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else:
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练习
练习1：英制单位英寸与公制单位厘米互换

"""
The British unit inch is interchanged with the metric unit centimeter
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"""
length = float(input('Please enter the length\n '))
unit = input('Please enter the unit\n')
if unit=='in':
    print('%fin = %fcm' % (length,length*2.54))
elif unit == 'cm':
    print('%fcm = %fin' % (length,length/2.54))
else:
    print('Please enter a valid unit')

练习2：百分制成绩转换为等级制成绩

"""
The hundred-mark system is converted to a hierarchical system
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"""
score = float(input('Please enter the score\n'))
if score >= 90:
    grade = 'A'
elif score >= 80:
    grade = 'B'
elif score >= 70:
    grade = 'C'
elif score >= 60:
    grade = 'D'
else:
    grade = 'E'
print('The corresponding level is',grade)

练习3：输入三条边长，如果能构成三角形就计算周长和面积

"""
Judge whether the input side length can form a triangle, 
if so, calculate the circumference and area of the triangle
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"""
a = float(input('a = '))
b = float(input('b = '))
c = float(input('c = '))
if a + b > c and a + c > b and b + c > a:
    C = (a + b + c ) / 2
    S = (C*(C-a)*(C-b)*(C-c))**0.5
    print('the circumference and area of the triangle is %f and %f' % (C,S))
else:
    print('You cannot make a triangle')