Python date formatting and plotting

Drawing a curve that changes over time is a requirement that is often encountered, such as a change in the number of software users. The function used to draw a curve that changes over time is matplotlib.pyplot.plot_date (date,num). Because its first variable is of type datetime, a format operation is required first for data entry of type string.

First, using Strptime to format the string 1.1 a basic example

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 Common format-specific correspondence

The common correspondence is shown in the following table (2014-12-28 13:49:30), more on Python for time-date formatting-go to Dawn-Blog Park

; ">year		month	day	hour		minute	second
%y	%y	%m	%b	%d	%h	%i	%m	%s
14	2014	12	Dec	28	13	01	49	30

Second specific drawing examples

Count the number of first-time installs of software in Windows and plot the scatter chart (by day) and histogram (yearly statistics)

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")PrintKeyall_software=[]k=0Try: I=0 while1: subkey_string=_winreg. EnumKey (key,i)#Print subkey_string        Try: J=0 Temp={} get_installdate=0#Some subkey may not be InstallDate subkey and value             while1:                #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                ifname=="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:Print forIteminchRange (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[' -']=0bar_by_year[' -']=0bar_by_year[' the']=0 forIteminchAll_software:ifCount.has_key (item["InstallDate"]): count[item["InstallDate"]]+=1Else: count[item["InstallDate"]]=1Bar_by_year[str (item['InstallDate'].year)]+=1xvalues=[]yvalues=[] forKey,valueinchCount.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, [' -',' -',' the'], rotation='Vertical') matplotlib.pyplot.show ()#value, type = _winreg. QueryValueEx (Key, "Enableautotray")

Iii. reference materials

[1] Python Operations Registry-unharmed-blog Park

[2]c++-How can I enumerate/list all installed applications in Windows XP? -Stack Overflow

[3]winreg–windows Registry Access-python v3.0.1 Documentation

[4]graph-plotting time in Python with Matplotlib-stack Overflow

[5] sha Hu King | Matplotlib Drawing 2

[6] Python chart drawing: Matplotlib Drawing library Get started-butterfly Meng Zhuang Zhou-Blog Park

[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

Python date formatting and plotting