python中time.time()和 time.strftime()：
time.time()返回的是一个浮点数，以秒为单位，time.strftime后可以自定义格式，如time.strftime('%Y-%m-%d %H:%M:%S')
#!/usr/bin/python
import time
t1 = time.time()
print t1
t2 = time.strftime('%Y-%m-%d %H:%M:%S')
print t2
:wq
今天、昨天、上月、去年：
#!/usr/bin/python
import time
today = time.strftime('%Y-%m-%d')
yesterday = time.localtime()[2]-1
last_month = time.localtime()[1]-1
last_year = time.localtime()[0]-1
print today
print yesterday
print last_month
print last_year
:wq
