画一个量随着时间变化的曲线是经常会遇到的需求，比如画软件用户数的变化曲线。画随时间变化的曲线主要用到的函数是matplotlib.pyplot.plot_date(date,num)。由于其第一个变量是datetime类型的，所以对于string类型的数据输入，首先需要进行格式化操作。
一、使用strptime进行string的格式化1.1一个基本例子 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常见的具体格式化对应关系 常见的对应关系如下表所示(2014-12-28 13:49:30)，更多可以参见python对时间日期做格式化 - 走到天亮 - 博客园
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、一个具体的画图例子统计windows下软件首次安装的数目并画出散点图(按日统计)和柱状图(按年统计)
import_winregimportdatetimeimportmatplotlib.datesimportmatplotlib.pyplotimportnumpy 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")printkey
all_software=[]
k=0try:
i=0while1:
subkey_string=_winreg.EnumKey(key,i)#print subkey_stringtry:
j=0
temp={}
get_installDate=0#some subkey may not have installdate subkey and valuewhile1:#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 "+nameifname=="DisplayName":#print "Name equals DisplayName"temp["DisplayName"]=valueifname=="InstallDate":#print "Name equals installdate"temp["InstallDate"]=value
get_installDate=1j+=1exceptWindowsError:#print 'interruptted j='+str(j)ifget_installDate:
all_software.append(temp)#print repr(name)#print valuei +=1exceptWindowsError:printforiteminrange(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']=0
bar_by_year['2013']=0
bar_by_year['2014']=0foriteminall_software:ifcount.has_key(item["InstallDate"]):
count[item["InstallDate"]]+=1else:
count[item["InstallDate"]]=1bar_by_year[str(item['InstallDate'].year)]+=1xvalues=[]
yvalues=[]forkey,valueincount.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")
三、参考材料[1]Python 操作注册表- 无恙 - 博客园
[2]c++ - How can I enumerate/list all installedapplications inWindows xp? - Stack Overflow
[3]winreg – Windows registryaccess— Python v3.0.1 documentation
[4]graph - plotting time in python with matplotlib - Stack Overflow
[5]沙湖王 | matplotlib绘图2
[6]Python图表绘制：matplotlib绘图库入门 - 蝶梦庄周 - 博客园
[7]ticks_and_spines example code: ticklabels_demo_rotation.py — Matplotlib 1.4.2 documentation
[8]api example code: barchart_demo.py — Matplotlib 1.4.2 documentation