小爬最近的一个需求是：将windows系统下的打印任务批量有序给到网络打印机。

用户先从公司的OA(B/S模式)系统下 打印指定内容的表单以及表单中的附件内容。这个问题可以这样分解：

1、抓包，得到OA对应的任务接口，然后利用python requests模拟post请求，获取所有的表单的URL并进行必要的去重处理；

2、打印OA表单的过程，需要浏览器在前台，这个时候可以结合selenium的driver.get(url)方法，打开每一个表单，同时解析网页内容，拿到所有附件的相关信息(名称、后缀、下载地址)，利用requests再度保存这些附件至本地；

3、打开表单后，利用 win32api.keybd_event，模拟键盘快捷键“Ctrl + Shift + P”调出系统的打印窗口；

4、选中“PDF打印机”，需要电脑中有“Microsoft Print to Pdf”或者“Foxit Reader PDF Printer”等；

5、利用pywin32中的相关方法，驱动打印过程，将每个OA表单(网页)打印成PDF文件并格式化命名＆存储，与前面的附件内容存储到同一个文件夹；

６、附件文件和OA生成的PDF文件均格式化存储，用OA单号作为文件名的一部分，将两者关联起来；

７、将本地对应文件夹的所有内容有序推送给打印机，指定打印机为某一台网络打印机。同时要确保打印过程中，不乱序；

针对步骤3，可以自定义函数来实现：

#键盘按下

defkey_down(keyname):

win32api.keybd_event(vk_code[keyname],0,0,0)#键盘抬起

defkey_up(key_name):

win32api.keybd_event(vk_code[key_name],0,win32con.KEYEVENTF_KEYUP,0)#按键组合操作

defsimulate_three_key(firstkey,sencondkey,lastkey):

key_down(firstkey)

key_down(sencondkey)

key_down(lastkey)

key_up(lastkey)

key_up(sencondkey)

key_up(firstkey)#按键组合操作

defsimulate_two_key(firstkey,sencondkey):

key_down(firstkey)

key_down(sencondkey)

key_up(sencondkey)

key_up(firstkey)

然后利用　simulate_three_key('ctrl',"shift",'p') 即可呼出系统的默认打印窗口：

那么步骤４，也就是上图的打印窗口，如何选中某一个打印机呢？直接利用win32gui.SendMessage

来选中某个打印机是非常困难的。一种可行的方法是，利用pywin32下的win32print模块，也就是本文的重点。

比如，用下面的代码可以遍历并获取到当前计算机的所有打印机信息：

for it in win32print.EnumPrinters(6):print(it[1])

我们甚至可以知道某台打印机的当前状态，假定某台打印机名为printerName，则可以这样获取打印机状态：

hPrinter =win32print.OpenPrinter (printerName)

dic= hex(win32print.GetPrinter(hPrinter,2)['Status'])if dic[-2]=="8":print("The printer is offline.")if dic[-5]=="4":print("The printer is out of toner.")elif dic[-5]=="2":print("The printer is low on toner.")

Printer status name/valueDescription

PRINTER_STATUS_BUSY

0x00000200

The printer is busy.

PRINTER_STATUS_DOOR_OPEN

0x00400000

The printer door is open.

PRINTER_STATUS_ERROR

0x00000002

The printer is in an error state.

PRINTER_STATUS_INITIALIZING

0x00008000

The printer is initializing.

PRINTER_STATUS_IO_ACTIVE

0x00000100

The printer is in an active input or output state.

PRINTER_STATUS_MANUAL_FEED

0x00000020

The printer is in a manual feed state.

PRINTER_STATUS_NOT_AVAILABLE

0x00001000

The printer is not available for printing.

PRINTER_STATUS_NO_TONER

0x00040000

The printer is out of toner.

PRINTER_STATUS_OFFLINE

0x00000080

The printer is offline.

PRINTER_STATUS_OUTPUT_BIN_FULL

0x00000800

The printer's output bin is full.

PRINTER_STATUS_OUT_OF_MEMORY

0x00200000

The printer has run out of memory.

PRINTER_STATUS_PAGE_PUNT

0x00080000

The printer cannot print the current page.

PRINTER_STATUS_PAPER_JAM

0x00000008

Paper is stuck in the printer.

PRINTER_STATUS_PAPER_OUT

0x00000010

The printer is out of paper.

PRINTER_STATUS_PAPER_PROBLEM

0x00000040

The printer has an unspecified paper problem.

PRINTER_STATUS_PAUSED

0x00000001

The printer is paused.

PRINTER_STATUS_PENDING_DELETION

0x00000004

The printer is being deleted as a result of a client's call to RpcDeletePrinter. No new jobs can be submitted on existing printer objects for that printer.

PRINTER_STATUS_POWER_SAVE

0x01000000

The printer is in power-save mode.<182>

PRINTER_STATUS_PRINTING

0x00000400

The printer is printing.

PRINTER_STATUS_PROCESSING

0x00004000

The printer is processing a print job.

PRINTER_STATUS_SERVER_OFFLINE

0x02000000

The printer is offline.<183>

PRINTER_STATUS_SERVER_UNKNOWN

0x00800000

The printer status is unknown.<184>

PRINTER_STATUS_TONER_LOW

0x00020000

The printer is low on toner.

PRINTER_STATUS_USER_INTERVENTION

0x00100000

The printer has an error that requires the user to do something.

PRINTER_STATUS_WAITING

0x00002000

The printer is waiting.

PRINTER_STATUS_WARMING_UP

0x00010000

The printer is warming up.

我们也可以得到当前默认的打印机，设置默认打印机：

currentPrinter=win32print.GetDefaultPrinterW()

win32print.SetDefaultPrinterW(printer)

我们利用上面两个函数，可以先得到系统当前的打印机，用变量存储后，再设置默认打印机至 PDF打印机，待执行完所有任务后，再设置默认打印机为用户一开始的默认打印机，整个过程用户不需要更多的干预；

重点说下步骤7：我们需要以OA表单+附件的形式，逐一给打印机分配任务，且不能乱序：

如果附件是图片性质，我们可以结合Pillow库来处理，示例代码如下：

importwin32printimportwin32uifrom PIL importImage, ImageWin#Constants for GetDeviceCaps#

#

#HORZRES / VERTRES = printable area#HORZRES = 8VERTRES= 10

#

#LOGPIXELS = dots per inch#LOGPIXELSX = 88LOGPIXELSY= 90

#

#PHYSICALWIDTH/HEIGHT = total area#PHYSICALWIDTH = 110PHYSICALHEIGHT= 111

#

#PHYSICALOFFSETX/Y = left / top margin#PHYSICALOFFSETX = 112PHYSICALOFFSETY= 113

defprint_image(file_name):

printer_name= win32print.GetDefaultPrinterW() #获得默认打印机

# #You can only write a Device-independent bitmap

#directly to a Windows device context; therefore

#we need (for ease) to use the Python Imaging

#Library to manipulate the image.

# #Create a device context from a named printer

#and assess the printable size of the paper.

# hDC =win32ui.CreateDC ()

hDC.CreatePrinterDC (printer_name)

printable_area=hDC.GetDeviceCaps (HORZRES), hDC.GetDeviceCaps (VERTRES)

printer_size=hDC.GetDeviceCaps (PHYSICALWIDTH), hDC.GetDeviceCaps (PHYSICALHEIGHT)

printer_margins=hDC.GetDeviceCaps (PHYSICALOFFSETX), hDC.GetDeviceCaps (PHYSICALOFFSETY)# #Open the image, rotate it if it's wider than

#it is high, and work out how much to multiply

#each pixel by to get it as big as possible on

#the page without distorting.

# bmp =Image.open (file_name)#bmp = bmp.rotate (90)

#bmp.save("test1.png")

if bmp.size[0] > bmp.size[1]:#bmp = bmp.rotate (90)

bmp=bmp.transpose(Image.ROTATE_90)

ratios= [1.0 * printable_area[0] / bmp.size[0], 1.0 * printable_area[1] / bmp.size[1]]

scale= min (ratios)*0.85 #这个0.85的系数是不希望图片被打印太大，缺少margin，不方便文档的装订file_name=file_name.split("\\")[-1] #这一步是为了提取fullpath中的filename部分# #Start the print job, and draw the bitmap to

#the printer device at the scaled size.

#hDC.StartDoc (file_name)

hDC.StartPage ()

dib=ImageWin.Dib (bmp)

scaled_width, scaled_height= [int (scale * i) for i inbmp.size]

x1= int ((printer_size[0] - scaled_width) / 2)

y1= int ((printer_size[1] - scaled_height) / 2)

x2= x1 +scaled_width

y2= y1 +scaled_height

dib.draw (hDC.GetHandleOutput (), (x1, y1, x2, y2))

hDC.EndPage ()

hDC.EndDoc ()

hDC.DeleteDC ()

需要强调的是，如果我们对图片进行后台旋转90度时，一定要用transpose(Image.ROTATE_90)，不要使用 rotate (90)，否则打印的图片很有可能显示不完整，且有黑边；

具体的transpose用法见Pillow官网文档：

如果我们要打印的任务是PDF或者其他office类型的文档，可以利用win32api.ShellExecute方法，示例如下：

defprinter_loading(filename):#open (filename, "r")

currentPrinter=win32print.GetDefaultPrinterW()

win32api.ShellExecute (0,"print",filename,'/d:"%s"' % currentPrinter,".",0)

该方法有一个缺陷，win32api.ShellExecute 会在指令发出后，立即返回值，而不是等打印任务真正传输到打印机后再返回。这就意味着，附件中的图片用win32ui的方法走后台已经传输给打印机，而PDF等其他文件可能还没及时发送给打印机，造成打印任务乱序。

可行的解决方法是，利用win32print.EnumJobs，定时获取打印机当前的任务队列，确保队列中出现刚推送的任务后，再来推送下一个打印任务。示例如下：

handle = win32print.OpenPrinter(printer_name).handle

tasks=win32print.EnumJobs(handle,0, -1, 1)

for task intasks:

taskName=task["pDocument"]

由于打印任务是动态增减的，每次得到的tasks可能都不同，且由于打印机可能有很多人共同使用，不能保证某个用户的某次打印任务一定会出现在打印队列的最上方。所以要尽可能拿到所有的任务；

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至此，这个项目中的难点都逐一有了解决方案，希望小爬以上的思路，对喜欢自动化的你，能有所借鉴~~