###### tags: `程式設計`
# 第二週
## 課堂練習一
輸入 float x1, x2
求 f(x) = x^3 在 x1 ~ x2 區間內的梯形面積
area = (x2 - x1) * (x2^3 + x1^3) / 2

x1, x2 = map(float,input().split())
print((x2-x1)*(x2**3+x1**3)/2)

## 課堂練習二
輸入float r, 代表圓的半徑
求面積

r  = float(input())
print(r*r*3.14159) #r**2

## 課堂練習三

#已知今年是2019
# input birthYear
# age = 2019 - birthYear
# if age >= 18
#     print adult
# else 
#     print child
birthYear = int(input())
if (2019 - birthYear >= 18):
    print('adult')
    print('your age is', 2019 - birthYear)
else:
    print('child')

## 判斷閏年 (條件式練習)
1. 西元年份除以4不可整除，為平年。
2. 西元年份除以4可整除，且除以100不可整除，為閏年。
3. 西元年份除以100可整除，且除以400不可整除，為平年
4. 西元年份除以400可整除，為閏年

# 3200年在 wiki上為平年
year = int(input('請輸入年分\n'))
if (year % 4 == 0 and year % 100 != 0) or (year % 400 == 0 and year % 3200 != 0):
    print('leap year')   
else :
    print('common year')

- using function

def isLeap(y):
    return y % 400 == 0 or (y %4 ==0 and y %100 != 0)

def main():
    year = int(input())
    if isLeap(year) :
        print ('leap year')
    else :
        print('common year')
if __name__ == '__main__':
    main()

## While Sample
- 輸出5~20

# while sample
def main():
    begin, end = 5, 20
    num = begin
    while num <= end:
        print(num)
        num = num + 1
if __name__ == '__main__':
    main()

- 印出星星(Square)

# input an int n 
# print square of size n
# eg n == 4
# ****
# ****
# ****
# ****
# how to think?
# (1) How many lines? n
# (2) if we give each line with id 'i', then
# line 1: how many *? n
# line 2: how many *? n
# line i: how many *? n
def main():
    n = int(input())
    num = 1
    while num <= n:                     print('*' * n)
        num +=1
if __name__ == '__main__':
    main()

- 印出星星 (Triangle)

# triangle
# *
# **
# ***
def main():
    size = int(input())
    linenum = 1
    while linenum <= size:
        print('*' * linenum)
        linenum +=1
if __name__ == '__main__':
    main()

- 印出星星 (Triangle)-前面增加空格

#    *
#   **
#  ***
def main():
    size = int(input())
    linenum = 1
    while linenum <= size:
        print(' ' * (size - linenum) + '*' * linenum)
        linenum +=1
if __name__ == '__main__':
    main()

- 印出星星 (Triangle)-正三角

#   *
#  ***
# *****
def main():
    size = int(input())
    linenum = 1
    while linenum <= size:
        print(' ' * (size - linenum) + '*' * (2*linenum-1))
        linenum +=1
if __name__ == '__main__':
    main()

## 補充
[Python 中的 if __name__ == '__main__' 該如何理解](http://blog.konghy.cn/2017/04/24/python-entry-program/)