python日期格式化與繪圖

2019-11-14 17:26:10

字體：大中小

供稿：網(wǎng)友

畫一個量隨著時間變化的曲線是經(jīng)常會遇到的需求，比如畫軟件用戶數(shù)的變化曲線。畫隨時間變化的曲線主要用到的函數(shù)是matplotlib.pyplot.plot_date(date,num)。由于其第一個變量是datetime類型的，所以對于string類型的數(shù)據(jù)輸入，首先需要進(jìn)行格式化操作。

一、使用strptime進(jìn)行string的格式化

1.1一個基本例子

time=datetime.datetime.strptime('2014-12-28 13:49:30','%Y-%m-%d %H:%M:%S')

　PRint time

2014-12-28 13:49:30

1.2常見的具體格式化對應(yīng)關(guān)系

常見的對應(yīng)關(guān)系如下表所示(2014-12-28 13:49:30)，更多可以參見python對時間日期做格式化 - 走到天亮 - 博客園

Year		Month		Day	Hour		Minute	Second
%y	%Y	%m	%b	%d	%H	%I	%M	%S
14	2014	12	Dec	28	13	01	49	30

二、一個具體的畫圖例子

統(tǒng)計windows下軟件首次安裝的數(shù)目并畫出散點圖(按日統(tǒng)計)和柱狀圖(按年統(tǒng)計)

import _winregimport datetimeimport matplotlib.datesimport matplotlib.pyplot import numpy as npprint "import winreg done!"key = _winreg.OpenKey(_winreg.HKEY_LOCAL_MACHINE,r"Software/Microsoft/Windows/CurrentVersion/Uninstall")#key = _winreg.OpenKey(_winreg.HKEY_CURRENT_USER,r"Software/Microsoft/Windows/CurrentVersion/Explorer")print keyall_software=[]k=0try:    i=0        while 1:        subkey_string=_winreg.EnumKey(key,i)        #print subkey_string        try:            j=0            temp={}            get_installDate=0            #some subkey may not have installdate subkey and value            while 1:                #subkey=_winreg.OpenKey(key,"InstallDate")                subkey=_winreg.OpenKey(key,subkey_string)                name, value, type_value = _winreg.EnumValue(subkey,j)                #print repr(name),repr(value)                #print "name is "+name                if name=="DisplayName":                    #print "Name equals DisplayName"                    temp["DisplayName"]=value                if name=="InstallDate":                    #print "Name equals installdate"                    temp["InstallDate"]=value                    get_installDate=1                j+=1        except WindowsError:            #print 'interruptted j='+str(j)            if get_installDate:                all_software.append(temp)        #print repr(name)        #print value        i +=1except WindowsError:    printfor item in range(len(all_software)):    all_software[item]["InstallDate"]=datetime.datetime.strptime(all_software[item]["InstallDate"].encode('ascii','ignore'),'%Y%m%d')count={}bar_by_year={}bar_by_year['2012']=0bar_by_year['2013']=0bar_by_year['2014']=0for item in all_software:    if count.has_key(item["InstallDate"]):        count[item["InstallDate"]]+=1    else:        count[item["InstallDate"]]=1    bar_by_year[str(item['InstallDate'].year)]+=1xvalues=[]yvalues=[]for key,value in count.iteritems():    xvalues.append(key)    yvalues.append(value)xvalues=matplotlib.dates.date2num(xvalues)matplotlib.pyplot.figure(1)matplotlib.pyplot.plot_date(xvalues,yvalues)matplotlib.pyplot.figure(2)xvalues_2=np.arange(3)yvalues_2=bar_by_year.values()fig2=matplotlib.pyplot.bar(xvalues_2,yvalues_2,0.5)matplotlib.pyplot.xticks(xvalues_2+0.25, ['2012','2013','2014'], rotation='vertical')matplotlib.pyplot.show()#value, type = _winreg.QueryValueEx(key, "EnableAutoTray")