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Two years ago when I started learning Python I had made a small note for myself as a quick reference which turned out to be so handy. The time I made the note I did not consider about sharing it. Now, after two years when I was working with Python for my Ubuntu Indicator Weather project, I was thinking maybe sharing the note could be useful for someone, though many better tutorials are available all over the Internet.
Apart from this post, as a Java developer I believe Python is one of the most beautiful languages, . Indeed I love it. It is easy to learn, code, and a great choice for RAD small projects.
Python scripts starts with the following line,
#!/us/bin/python
Defining a variable
x = 10
print x
Python loosely typed language, means you do not need to specify the type of variables.
Working with strings:
str = "ABCDE"
print string[0] # A
print String[0:1] # AB
print String[1:] # BCDE
Lists:
lst = ['a',1,'qq']
len(lst) >>> 3
Maps:
v = {'key1':'value', 1:2}
Saving Python interaction into a file after writing your program
import readline
readline.write_history_file("path_of_the_file")
Getting ascii code of char:
ord('A')
Getting hexadecimal of a decimal number:
hex(123)
Getting octal of a decimal number:
oct(11)
Start variable or method with underscore means private, with two __ means too private.
Power :
2**3 # 8
If structure
if x <> 10:
print "x is not 10"
elif x == 2:
print "x is 2"
else:
print "x is not 10 or 2"
Bubble sort (for loop):
arr = [10,79,4,12,80,100,400]
for cnt in range(len(arr)):
... for cnt1 in range(cnt+1,len(arr)):
... if(arr[cnt]>arr[cnt1]):
... swap = arr[cnt]
... arr[cnt] = arr[cnt1]
... arr[cnt1] = swap
...
print arr # [4, 10, 12, 79, 80, 100, 400]
Pass is like ; (null instruction) in the C style language:
if(x == y);
if x == y: pass
Getting maximum and minimum value of a list:
max(list)
min(list)
More amazing stuff with lists:
choice(list) # Get a random number from the list
randrange(10) # Generate a random number
Randomizing the items of a list in place.
import random
random.shuffle(list);
print list;
Keyword arguments:
#!/usr/bin/python
# Function definition is here
def printinfo( name, age )
print "Name: ", name
print "Age ", age
# Now you can call printinfo function
printinfo( age=50, name="miki" ) # Name: miki, Age: 50
Default argument:
#!/usr/bin/python
# Function definition is here
def printinfo( name, age = 35 ):
print "Name: ", name
print "Age ", age
# Now you can call printinfo function
printinfo( age=50, name="miki" ) # Name: miki, Age 50
printinfo( name="miki" ) # Name: miki, Age 35
Variable-length arguments:
#!/usr/bin/python
# Function definition is here
def printinfo( arg1, *vartuple ):
print "Output is: "
print arg1
for var in vartuple:
print var
# Now you can call printinfo function
printinfo( 10 )
printinfo( 70, 60, 50 )
Lambda expression or anonymous function
lambda [arg1 [,arg2,.....argn]]:expression
sum = lambda x,y,z,q: x*y*z*y
The dir() built-in function returns a sorted list of strings containing the names defined by a module.
dir(importModuleName);
