Basic introduction to Python2.5 and 2.6

Start walking

 
#! /usr/bin/python 

a=2 
b=3 
c="test" 
c=a+b 
print "execution result: %i"%c 

knowledge

Python is a dynamic language, and variables do not have to be declared in advance.
Print statements in C style
Strings and Numbers
But the interesting thing is that in javascript we would ideally link strings to Numbers, of course, because it's a dynamic language, but in Python it's a little weird, like this:

 
#! /usr/bin/python 

a=2 
b="test" 
c=a+b 

Running this line of code causes an error that tells you that strings and Numbers cannot be connected, so you have to use the built-in function to convert

 
#! /usr/bin/python 

a=2 
b="test" 
c=str(a)+b 
d="1111" 
e=a+int(d) 
#How to print multiply values 
print "c is %s,e is %i" % (c,e) 

Knowledge:

Converts strings and Numbers using the int and STR functions
Print begins with #, not the customary //
How to print multiple parameters
internationalization
Tired of writing English notes, we need to use Chinese!


#! The/usr/bin/python
# -*- coding: utf8 -*-

"God returns: diego maradona takes over as Argentina coach."
Knowledge:

Add character set to use Chinese
The list of
Lists are javascript-like arrays that are easy to use

 

#! /usr/bin/python 
# -*- coding: utf8 -*- 

# Define a tuple  
word=['a','b','c','d','e','f','g'] 

# How do I access elements in a tuple by index  
a=word[2] 
print "a is: "+a 
b=word[1:3] 
print "b is: " 
print b # index 1 and 2 elements of word. 
c=word[:2] 
print "c is: " 
print c # index 0 and 1 elements of word. 
d=word[0:] 
print "d is: " 
print d # All elements of word. 

# Tuples can be merged  
e=word[:2]+word[2:] 
print "e is: " 
print e # All elements of word. 
f=word[-1] 
print "f is: " 
print f # The last elements of word. 
g=word[-4:-2] 
print "g is: " 
print g # index 3 and 4 elements of word. 
h=word[-2:] 
print "h is: " 
print h # The last two elements. 
i=word[:-2] 
print "i is: " 
print i # Everything except the last two characters 
l=len(word) 
print "Length of word is: "+ str(l) 
print "Adds new element" 
word.append('h') 
print word 

# Remove elements  
del word[0] 
print word 
del word[1:3] 
print word 

Knowledge:

The list length is dynamic and you can add and remove elements at will.
Indexes make it easy to access elements or even return a sublist
Refer to the Python documentation for more methods
The dictionary

 
#! /usr/bin/python 

x={'a':'aaa','b':'bbb','c':12} 
print x['a'] 
print x['b'] 
print x['c'] 

for key in x: 
print "Key is %s and value is %s",(key,x[key]) 

keys=x.items(); 
print keys[0] 
keys[0]='ddd' 
print keys[0] 

Knowledge:

Use it as a Java Map.
string
The way Python handles strings is more impressive than C/C++. Use strings as lists.

 
word="abcdefg" 
a=word[2] 
print "a is: "+a 
b=word[1:3] 
print "b is: "+b # index 1 and 2 elements of word. 
c=word[:2] 
print "c is: "+c # index 0 and 1 elements of word. 
d=word[0:] 
print "d is: "+d # All elements of word. 
e=word[:2]+word[2:] 
print "e is: "+e # All elements of word. 
f=word[-1] 
print "f is: "+f # The last elements of word. 
g=word[-4:-2] 
print "g is: "+g # index 3 and 4 elements of word. 
h=word[-2:] 
print "h is: "+h # The last two elements. 
i=word[:-2] 
print "i is: "+i # Everything except the last two characters 
l=len(word) 
print "Length of word is: "+ str(l) 

Note the difference between Asc and Unicode strings:

 
#! /usr/bin/python 
# -*- coding: utf8 -*- 

s=raw_input(" Enter your Chinese name , Press enter to continue "); 
print " Your name is  : " +s; 

l=len(s) 
print " The length of your Chinese name is :"+str(l); 
a=unicode(s,"utf8") 
l=len(a) 
print " I'm sorry , There was a calculation error . We should use utf8 To calculate the length of the Chinese string ,  
 The length of your name should be :"+str(l); 

Knowledge:

Transcoding using unicode functions
Conditions and loops

 
#! /usr/bin/python 
x=int(raw_input("Please enter an integer:")) 
if x<0: 
x=0 
print "Negative changed to zero" 

elif x==0: 
print "Zero" 

else: 
print "More" 


# Loops List 
a = ['cat', 'window', 'defenestrate'] 
for x in a: 
print x, len(x) 

Knowledge:

Conditions and loops
How do I get console input
function

 
#! /usr/bin/python 
# -*- coding: utf8 -*- 

def sum(a,b): 
return a+b 


func = sum 
r = func(5,6) 
print r 

#  Provide default values  
def add(a,b=2): 
return a+b 
r=add(1) 
print r 
r=add(1,5) 
print r 

A nice function

 
#! /usr/bin/python 
# -*- coding: utf8 -*- 

# The range() function 
a =range(5,10) 
print a 
a = range(-2,-7) 
print a 
a = range(-7,-2) 
print a 
a = range(-2,-11,-3) # The 3rd parameter stands for step 
print a 

Knowledge:

Python doesn't use {} to control the program structure. It forces you to indent the program to make the code clear.
It's easy to define functions
Handy range function
Exception handling

 
#! /usr/bin/python 
s=raw_input("Input your age:") 
if s =="": 
raise Exception("Input must no be empty.") 

try: 
i=int(s) 
except ValueError: 
print "Could not convert data to an integer." 
except: 
print "Unknown exception!" 
else: # It is useful for code that must be executed if the try clause does not raise an exception 
print "You are %d" % i," years old" 
finally: # Clean up action 
print "Goodbye!"