How to read keyboard-input

Question

I would like to read data from the keyboard in python  I try this   nb   input  Choose a number   print   Number s  n     nb     But it doesn t work  neither with eclipse nor in the terminal  it s always stop of the question  I can type a number but after nothing happen   Do you know why

User · Answer

try   raw input  Enter your input       If you use Python 2 input  Enter your input           If you use Python 3   and if you want to have a numeric value  just convert it    try      mode int raw input  Input     except ValueError      print  Not a number

User · Answer

It seems that you are mixing different Pythons here  Python 2 x vs  Python 3 x     This is basically correct   nb   input  Choose a number       The problem is that it is only supported in Python 3  As  sharpner answered  for older versions of Python  2 x   you have to use the function raw input   nb   raw input  Choose a number       If you want to convert that to a number  then you should try   number   int nb        though you need to take into account that this can raise an exception   try      number   int nb  except ValueError      print  Invalid number     And if you want to print the number using formatting  in Python 3 str format   is recommended   print  Number   0  n  format number     Instead of   print  Number  s  n     nb     But both options  str format   and    do work in both Python 2 7 and Python 3

User · Answer

Non-blocking  multi-threaded example  As blocking on keyboard input  since the input   function blocks  is frequently not what we want to do  we d frequently like to keep doing other stuff   here s a very-stripped-down multi-threaded example to demonstrate how to keep running your main application while still reading in keyboard inputs whenever they arrive  This works by creating one thread to run in the background  continually calling input   and then passing any data it receives to a queue  In this way  your main thread is left to do anything it wants  receiving the keyboard input data from the first thread whenever there is something in the queue  1  Bare Python 3 code example  no comments   import threading import queue import time  def read kbd input inputQueue       print  Ready for keyboard input        while  True           input str   input           inputQueue put input str   def main        EXIT COMMAND    quot exit quot      inputQueue   queue Queue        inputThread   threading Thread target read kbd input  args  inputQueue    daemon True      inputThread start        while  True           if  inputQueue qsize    gt  0               input str   inputQueue get               print  quot input str      quot  format input str                if  input str    EXIT COMMAND                   print  quot Exiting serial terminal  quot                   break                            Insert your code here to do whatever you want with the input str             The rest of your program goes here           time sleep 0 01       print  quot End  quot    if    name         main           main    2  Same Python 3 code as above  but with extensive explanatory comments   quot  quot  quot  read keyboard input py  Gabriel Staples www ElectricRCAircraftGuy com 14 Nov  2018  References  - https   pyserial readthedocs io en latest pyserial api html -      https   www tutorialspoint com python python multithreading htm -      https   en wikibooks org wiki Python Programming Threading - https   stackoverflow com questions 1607612 python-how-do-i-make-a-subclass-from-a-superclass - https   docs python org 3 library queue html - https   docs python org 3 7 library threading html  To install PySerial   sudo python3 -m pip install pyserial   To run this program   python3 this filename py    quot  quot  quot   import threading import queue import time  def read kbd input inputQueue       print  Ready for keyboard input        while  True             Receive keyboard input from user          input str   input                      Enqueue this input string            Note  Lock not required here since we are only calling a single Queue method  not a sequence of them            which would otherwise need to be treated as one atomic operation          inputQueue put input str   def main         EXIT COMMAND    quot exit quot    Command to exit this program        The following threading lock is required only if you need to enforce atomic access to a chunk of multiple queue       method calls in a row   Use this if you have such a need  as follows        1  Pass queueLock as an input parameter to whichever function requires it        2  Call queueLock acquire   to obtain the lock        3  Do your series of queue calls which need to be treated as one big atomic operation  such as calling       inputQueue qsize    followed by inputQueue put    for example        4  Call queueLock release   to release the lock        queueLock   threading Lock          Keyboard input queue to pass data from the thread reading the keyboard inputs to the main thread      inputQueue   queue Queue          Create  amp  start a thread to read keyboard inputs        Set daemon to True to auto-kill this thread when all other non-daemonic threads are exited  This is desired since       this thread has no cleanup to do  which would otherwise require a more graceful approach to clean up then exit      inputThread   threading Thread target read kbd input  args  inputQueue    daemon True      inputThread start          Main loop     while  True              Read keyboard inputs           Note  if this queue were being read in multiple places we would need to use the queueLock above to ensure           multi-method-call atomic access  Since this is the only place we are removing from the queue  however  in this           example program  no locks are required          if  inputQueue qsize    gt  0               input str   inputQueue get               print  quot input str      quot  format input str                if  input str    EXIT COMMAND                   print  quot Exiting serial terminal  quot                   break   exit the while loop                            Insert your code here to do whatever you want with the input str             The rest of your program goes here             Sleep for a short time to prevent this thread from sucking up all of your CPU resources on your PC          time sleep 0 01            print  quot End  quot      If you run this Python file directly  ex  via  python3 this filename py    do the following  if    name         main           main    Sample output     python3 read keyboard input py Ready for keyboard input  hey input str   hey hello input str   hello 7000 input str   7000 exit input str   exit Exiting serial terminal  End   The Python Queue library is thread-safe  Note that Queue put   and Queue get   and other Queue class methods are thread-safe  That means they implement all the internal locking semantics required for inter-thread operations  so each function call in the queue class can be considered as a single  atomic operation  See the notes at the top of the documentation  https   docs python org 3 library queue html  emphasis added    The queue module implements multi-producer  multi-consumer queues  It is especially useful in threaded programming when information must be exchanged safely between multiple threads  The Queue class in this module implements all the required locking semantics   References   https   pyserial readthedocs io en latest pyserial api html      https   www tutorialspoint com python python multithreading htm      https   en wikibooks org wiki Python Programming Threading Python  How do I make a subclass from a superclass  https   docs python org 3 library queue html https   docs python org 3 7 library threading html  Related Cross-Linked   PySerial non-blocking read loop

[python] How to read keyboard-input?

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