Simple text game with Python

In this article we will demonstrate how to create a simple guessing game.  
The goal of the game is to guess the right number.

Example
An example run below:

python-text-game
Simple text game with Python

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Random number

The user will be asked to guess the random number. We first pick the random number:

from random import randint
 
x = randint(1,9)

The randint() function will pick a pseudo random number between 1 and 10. Then we have to continue until the correct number is found:

guess = -1
 
print("Guess the number below 10:")
while guess != x:
    guess = int(raw_input("Guess: "))
 
    if guess != x:
        print("Wrong guess")
    else:
        print("Guessed correctly")

Python Guessing Game

The code below starts the game:

from random import randint
 
x = randint(1,9)
guess = -1
 
print "Guess the number below 10:"
while guess != x:
    guess = int(raw_input("Guess: "))
 
    if guess != x:
        print("Wrong guess")
    else:
        print("Guessed correctly")

An example run:

Guess the number below 10:
Guess: 3
Wrong guess
Guess: 6
Wrong guess
..

Python network sockets programming tutorial

In this tutorial you will learn about in network programming. You will learn about the client-server model that is in use for the World Wide Web, E-mail and many other applications.

client server
Client server (with email protocol)
The client server model is a model where there are n clients and one server. The clients make  data requests to a server. The server replies to those messages received. A client can be any device such as  your computer or tablet. Servers are generally dedicated computers which are to be connected 24/7. 

Related course:
If you prefer a course or certification:

socket server code

This code will start a simple web server using sockets. It waits for a connection and if a connection is received it will output the bytes received.

#!/usr/bin/env python
 
import socket
 
TCP_IP = '127.0.0.1'
TCP_PORT = 62
BUFFER_SIZE = 20  # Normally 1024, but we want fast response
 
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((TCP_IP, TCP_PORT))
s.listen(1)
 
conn, addr = s.accept()
print 'Connection address:', addr
while 1:
     data = conn.recv(BUFFER_SIZE)
     if not data: break
     print "received data:", data
     conn.send(data)  # echo
conn.close()

Execute with:

$ python server.py

This opens the web server at port 62. In a second screen, open a client with Telnet. If you use the same machine for the client and server use:

$ telnet 127.0.0.1 62.

If you use another machine as client, type the according IP address of that machine. You can find it with ifconfig.

Everything you write from the client will arrive at the server. The server sends the received messages back. An example output below (Click to enlarge):

socket network client:

The client script below sends a message to the server. The server must be running!

#!/usr/bin/env python
 
import socket
 
 
TCP_IP = '127.0.0.1'
TCP_PORT = 5005
BUFFER_SIZE = 1024
MESSAGE = "Hello, World!"
 
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((TCP_IP, TCP_PORT))
s.send(MESSAGE)
data = s.recv(BUFFER_SIZE)
s.close()
 
print "received data:", data

This client simply mimics the behavior we did in Telnet.

Limitations of the server code
The server code above can only interact with one client.  If you try to connect with a second terminal it simply won’t reply to the new client. To let the server interact with multiple clients you need to use multi-threading. We rebuild the server script to accept multiple client connections:

#!/usr/bin/env python
 
import socket
from threading import Thread
from SocketServer import ThreadingMixIn
 
class ClientThread(Thread):
 
    def __init__(self,ip,port):
        Thread.__init__(self)
        self.ip = ip
        self.port = port
        print "[+] New thread started for "+ip+":"+str(port)
 
 
    def run(self):
        while True:
            data = conn.recv(2048)
            if not data: break
            print "received data:", data
            conn.send(data)  # echo
 
TCP_IP = '0.0.0.0'
TCP_PORT = 62
BUFFER_SIZE = 20  # Normally 1024, but we want fast response
 
 
tcpsock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
tcpsock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
tcpsock.bind((TCP_IP, TCP_PORT))
threads = []
 
while True:
    tcpsock.listen(4)
    print "Waiting for incoming connections..."
    (conn, (ip,port)) = tcpsock.accept()
    newthread = ClientThread(ip,port)
    newthread.start()
    threads.append(newthread)
 
for t in threads:
    t.join()

Application protocol

So far we have simply sent messages back and forth. Every message can have a specific meaning in an application. This is known as the protocol.  The meaning of these messages must be the same on both the sender and receiver side.  The Transport Layer below makes sure that messages are received (TCP). The Internet Layer is the IPv4 protocol.  All we have to define is the Application Layer.

Below we modified the server to accept simple commands (We use the non-threading server for simplicity). We changed the port to 64.  Server code with a protocol:

#!/usr/bin/env python
 
import socket
 
TCP_IP = '127.0.0.1'
TCP_PORT = 64
BUFFER_SIZE = 20  # Normally 1024, but we want fast response
 
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((TCP_IP, TCP_PORT))
s.listen(1)
 
conn, addr = s.accept()
print 'Connection address:', addr
while 1:
     data = conn.recv(BUFFER_SIZE)
     if not data: break
     print "received data:", data
     #conn.send(data)  # echo
     if "/version" in data:
         conn.send("Demo versionn")
 
     if "/echo" in data:
         data = data.replace("/echo","")
         conn.send(data + "n")
 
conn.close()

Run the server with:

sudo python server.py

A client can then connect with telnet (make sure you pick the right IP):

$ telnet 127.0.0.1 64
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.
message
/version
Demo version
/echo Repeat this
 Repeat this

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JSON encoding and decoding with Python

Introduction
JSON (JavaScript Object Notation) is frequently used between a server and a web application. An example of JSON data:

{
    "persons": [
        {
            "city": "Seattle", 
            "name": "Brian"
        }, 
        {
            "city": "Amsterdam", 
            "name": "David"
        }
    ]
}

The json module enables you to convert between JSON and Python Objects.

JSON conversion examples

Convert JSON to Python Object (Dict)
To convert JSON to a Python dict use this:

import json
 
json_data = '{"name": "Brian", "city": "Seattle"}'
python_obj = json.loads(json_data)
print python_obj["name"]
print python_obj["city"]

Convert JSON to Python Object (List)
JSON data can be directly mapped to a Python list.

import json
 
array = '{"drinks": ["coffee", "tea", "water"]}'
data = json.loads(array)
 
for element in data['drinks']:
    print element

Convert JSON to Python Object (float)
Floating points can be mapped using the decimal library.

import json
from decimal import Decimal
 
jsondata = '{"number": 1.573937639}'
 
x = json.loads(jsondata, parse_float=Decimal)
print x['number']

Convert JSON to Python Object (Example)
JSON data often holds multiple objects, an example of how to use that below:

import json
 
json_input = '{"persons": [{"name": "Brian", "city": "Seattle"}, {"name": "David", "city": "Amsterdam"} ] }'
 
try:
    decoded = json.loads(json_input)
 
    # Access data
    for x in decoded['persons']:
        print x['name']
 
except (ValueError, KeyError, TypeError):
    print "JSON format error"

Convert Python Object (Dict) to JSON
If you want to convert a Python Object to JSON use the json.dumps() method.

import json
from decimal import Decimal
 
d = {}
d["Name"] = "Luke"
d["Country"] = "Canada"
 
print json.dumps(d, ensure_ascii=False)
# result {"Country": "Canada", "Name": "Luke"}

Converting JSON data to Python objects 
JSON data can be converted (deserialized) to Pyhon objects using the json.loads() function.  A table of the mapping:

JSON Python
object dict
array list
string str
number (int) int
number (real) float
true True
false False
null None

Pretty printing

If you want to display JSON data you can use the json.dumps() function.

import json
 
json_data = '{"name": "Brian", "city": "Seattle"}'
python_obj = json.loads(json_data)
print json.dumps(python_obj, sort_keys=True, indent=4)

More
Google Charts with JSON data

Menu with PyQt4

PyQT Menu pythonspot
PyQT Menu

PyQt4 menus appear in the top of the window bar. A menu gives the user control over the application and is often location in the top of the window.

The QMainWindow class creates the main application window. This class has a method named menuBar() which adds the title bar.

Menus can be added to the title bar using addMenu(). Inside each menu you can add a command using the addAction method.

Related course:

PyQt4 menubar

This code will add a menu to your qt4 app:

#! /usr/bin/env python
# -*- coding: utf-8 -*-
#
import sys
from PyQt4.QtGui import *
 
# Create an PyQT4 application object.
a = QApplication(sys.argv)
 
# The QWidget widget is the base class of all user interface objects in PyQt4.
w = QMainWindow()
 
# Set window size.
w.resize(320, 240)
 
# Set window title
w.setWindowTitle("Hello World!")
 
# Create main menu
mainMenu = w.menuBar()
mainMenu.setNativeMenuBar(False)
fileMenu = mainMenu.addMenu('&File')
 
# Add exit button
exitButton = QAction(QIcon('exit24.png'), 'Exit', w)
exitButton.setShortcut('Ctrl+Q')
exitButton.setStatusTip('Exit application')
exitButton.triggered.connect(w.close)
fileMenu.addAction(exitButton)
 
# Show window
w.show()
 
sys.exit(a.exec_())

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QT4 Widgets

We have various widgets that we can access with PyQT. Including:

  • Textbox
  • Combobox
  • Calendar

For more widgets we suggest using the GUI creation tool covered in the next tutorial.

Related course:

Textbox widget
Input fields are present in nearly every application. In PyQT4 an input field can be created using the QLineEdit() function.

#! /usr/bin/env python
# -*- coding: utf-8 -*-
#
import sys
from PyQt4.QtGui import *
 
# Create an PyQT4 application object.
a = QApplication(sys.argv)
 
# The QWidget widget is the base class of all user interface objects in PyQt4.
w = QMainWindow()
 
# Set window size.
w.resize(320, 100)
 
# Set window title
w.setWindowTitle("PyQT Python Widget!")
 
# Create textbox
textbox = QLineEdit(w)
textbox.move(20, 20)
textbox.resize(280,40)
 
# Show window
w.show()
 
sys.exit(a.exec_())
qt textbox
qt textbox

Combobox
A combobox can be used to select an item from a list.

#! /usr/bin/env python
# -*- coding: utf-8 -*-
#
import sys
from PyQt4.QtGui import *
 
# Create an PyQT4 application object.
a = QApplication(sys.argv)
 
# The QWidget widget is the base class of all user interface objects in PyQt4.
w = QMainWindow()
 
# Set window size.
w.resize(320, 100)
 
# Set window title
w.setWindowTitle("PyQT Python Widget!")
 
# Create combobox
combo = QComboBox(w)
combo.addItem("Python")
combo.addItem("Perl")
combo.addItem("Java")
combo.addItem("C++")
combo.move(20,20)
 
# Show window
w.show()
 
sys.exit(a.exec_())
qt combobox
qt combobox

Calendar widget
The PyQT4 library has a calendar widget, you can create it using the QCalendarWidget() call.

#! /usr/bin/env python
# -*- coding: utf-8 -*-
#
import sys
from PyQt4.QtGui import *
 
# Create an PyQT4 application object.
a = QApplication(sys.argv)
 
# The QWidget widget is the base class of all user interface objects in PyQt4.
w = QMainWindow()
 
# Set window size.
w.resize(320, 240)
 
# Set window title
w.setWindowTitle("PyQT Python Widget!")
 
# Create calendar
cal = QCalendarWidget(w)
cal.setGridVisible(True)
cal.move(0, 0)
cal.resize(320,240)
 
# Show window
w.show()
 
sys.exit(a.exec_())

Result:

calendar qt
calendar qt

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