学步园

from datetime import datetime
from datetime import timedelta
import calendar

def getFirstDayOfLastMonth():
    d = datetime.now()
    c = calendar.Calendar()
    
    year = d.year
    month = d.month
    
    if month == 1 :
        month = 12
        year -= 1
    else :
        month -= 1
    return datetime(year,month,1).strftime('%Y-%m-%d %X') 

计算天数：

函数：
calendar.monthrange(year, month)
Returns weekday of first day of the month and number of days 
in month, for the specified year and month.

实例：

>>> import calendar
>>> now_year=2012
>>> now_month=7
>>> calendar.monthrange(now_year,now_month)
(6, 31)
>>> calendar.monthrange(now_year,now_month)[1]
31