python references

Reference Cards
http://www.astro.up.pt/~sousasag/Python_For_Astronomers/Python_qr.pdf

Regular expression
https://developers.google.com/edu/python/regular-expressions?hl=en


Python Basics

Python has five standard data types −

- Numbers
- String
- List
- Tuple
- Dictionary

### Strings
str = 'Hello World!'

print str          # Prints complete string
print str[0]       # Prints first character of the string
print str[2:5]     # Prints characters starting from 3rd to 5th
print str[2:]      # Prints string starting from 3rd character
print str * 2      # Prints string two times
print str + "TEST" # Prints concatenated string


### List
list = [ 'abcd', 786 , 2.23, 'john', 70.2 ]
tinylist = [123, 'john']

print list          # Prints complete list
print list[0]       # Prints first element of the list
print list[1:3]     # Prints elements starting from 2nd till 3rd 
print list[2:]      # Prints elements starting from 3rd element
print tinylist * 2  # Prints list two times
print list + tinylist # Prints concatenated lists
del list1[2];
len([1, 2, 3])
[1, 2, 3] + [4, 5, 6]
3 in [1, 2, 3]
for x in [1, 2, 3]: print x


### Tuple
They are readonly
tuple = ( 'abcd', 786 , 2.23, 'john', 70.2  )
tinytuple = (123, 'john')

print tuple           # Prints complete list
print tuple[0]        # Prints first element of the list
print tuple[1:3]      # Prints elements starting from 2nd till 3rd 
print tuple[2:]       # Prints elements starting from 3rd element
print tinytuple * 2   # Prints list two times
print tuple + tinytuple # Prints concatenated lists
len((1, 2, 3))
(1, 2, 3) + (4, 5, 6)
3 in (1, 2, 3)
for x in (1, 2, 3): print x



### Dictionary
Python's dictionaries are kind of hash table type
dict = {}
dict['one'] = "This is one"
dict[2]     = "This is two"
del dict['one']; 

tinydict = {'name': 'john','code':6734, 'dept': 'sales'}


print dict['one']       # Prints value for 'one' key
print dict[2]           # Prints value for 2 key
print tinydict          # Prints complete dictionary
print tinydict.keys()   # Prints all the keys
print tinydict.values() # Prints all the values

len(dict)
seq = ('name', 'age', 'sex')
dict = dict.fromkeys(seq)
dict.has_key(key)
dict.items() # Returns a list of dict's (key, value) tuple pairs
dict.keys()
dict.values()
dict.update(dict2)


### Python Membership Operators
Python’s membership operators test for membership in a sequence, such as strings, lists, or tuples.
x in y
x not in y

### Python Identity Operators
Identity operators compare the memory locations of two objects. Both should be poiting to same object
x is y
x is not y


str.find(str2, beg=0 end=len(string))
"-".join("a","b","c")
str.split(str=" ")
str.splitlines()
str.strip()


### Functions arguments are passed by reference
def changeme( mylist ):
   "This changes a passed list into this function"
   mylist.append([1,2,3,4]);
   print "Values inside the function: ", mylist
   return

# Now you can call changeme function
mylist = [10,20,30];
changeme( mylist );
print "Values outside the function: ", mylist
Values inside the function:  [10, 20, 30, [1, 2, 3, 4]]
Values outside the function:  [10, 20, 30, [1, 2, 3, 4]]


### Default value
def printinfo( name, age = 35 ):
Variable args
def printinfo( arg1, *vartuple ):
	for var in vartuple:
      		print var
# Now you can call printinfo function
printinfo( 70, 60, 50 )


### Module import
import module1[, module2[,... moduleN]
from modname import name1[, name2[, ... nameN]]
# Now import your Phone Package.
import Phone
Phone.Pots()
Phone.Isdn()
Phone.G3()


input
str = input("Enter your input: ");

[x*5 for x in range(2,10,2)]

fo = open("foo.txt", "r")
str = fo.read(10);
fo.close()