題目：輸入某年某月某日，判斷這一天是這一年的第幾天？

程式分析：以3月5日為例，應該先把前兩個月的加起來，然後再加上5天即本年的第幾天，特殊情況，閏年且輸入月份大於2時需考慮多加一天：

year=int(input("請輸入年份：\n"))
month=int(input("請輸入月份：\n"))
day=int(input("請輸入天數：\n"))
months = (0,31,59,90,120,151,181,212,243,273,304,334)
if 0 <month <=12:
    sum=months[month-1]
else:
    print("輸入錯誤！！")
sum 
 
+=day
leap =0
if (year%400==0) or ((year%4==0) and (year%100!=0)):
    leap=1
if (leap==1) and (month>2):
    sum+=1
print(year,month,day,'是%dth 天.' % sum)

結果是：

C:\Anaconda3\python.exe "C:\Program Files\JetBrains\PyCharm 2019.1.1\helpers\pydev\pydevconsole.py" --mode=client --port=58506
import sys; print
 
('Python %s on %s' % (sys.version, sys.platform))
sys.path.extend(['C:\\app\\PycharmProjects', 'C:/app/PycharmProjects'])
Python 3.7.6 (default, Jan  8 2020, 20:23:39) [MSC v.1916 64 bit (AMD64)]
Type 'copyright', 'credits' or 'license' for more information
IPython 7.12.0 -- An enhanced Interactive Python. Type '
 
?' for help.
PyDev console: using IPython 7.12.0
Python 3.7.6 (default, Jan  8 2020, 20:23:39) [MSC v.1916 64 bit (AMD64)] on win32
runfile('C:/app/PycharmProjects/tensorflow/test.py', wdir='C:/app/PycharmProjects/tensorflow')
請輸入年份：
2020
請輸入月份：
10
請輸入天數：
20
2020 10 20 是294th 天.