Python data-types

Some Python Data types

Strings

In short strings are a bunch of letters or numbers inside quotation marsk (either single or double).

Learn more in http://interactivepython.org/courselib/static/thinkcspy/Strings/toctree.html#strings

s="I am a string" #assign string to variable s

# some String methods and opertations:
print '.upper():', s.upper()
print '.replace():', s.replace('string', 'bunch of letters or numbers inside quotations')

print '.startswith()', s.startswith('I') 
print  '.endswith()',s.endswith('strings') 
print 'integer to string:', str(2)
print 'adding strings:', s + " " + "in python" + " " + str(2)
print '.split():',s.split(' ') # split string to list at empty space ' '

Lists

Are collections of python data values, each element is identified by an index corresponding to its position in the list.

Lists are writen with square brackets and contain different data-types (integer,floats,strings,lists,etc) inside one list.

Learn more in http://interactivepython.org/courselib/static/thinkcspy/Lists/toctree.html

# Lists
l = [10, 100, 'a string']
print l
print 'element at index 1:', l[1] 
print 'index of element "a string":', l.index("a string")
print 'lenght of string:', len(l)

l.append('another string')
l.append([1,2,3]) # appending a list to the list
print 'expanded list:',l

l.remove(10)
print 'reduced list:',l

# list creation
print 'a list from 0 to 19:', range(20)

Dictionaries

Dictionaries or objects a like lists. They store data of different type. The major difference bieng: * lists store data in sequences, whose values are accessed using its index position * dictionaries storage data in key:value pairs, whose values are accessed using the key

Like lists it allows many data-types: numbers (integer or float), strings, lists, dictionaries (a dictionary containing a dictionary), Null (An empty value)

More on Python dictionaries

• https://docs.python.org/2/tutorial/datastructures.html#dictionaries
• http://interactivepython.org/courselib/static/thinkcspy/Dictionaries/toctree.html

# create a dictionary
piratelibs = {'Memory_or_the_World':'Marcel Mars',
    'aaaarg': 'Sea Dockray',
     'Monoskop':'Dusan Barok',
     'Sci-hub': 'Alexandra Elbakyan'
    }
scihub = piratelibs['Sci-hub'] # access one of its keys
print scihub

# add a new key do the dictionary
piratelibs['WPB']='WORM'

# loop trhough all the dictionary keys
for k in piratelibs.keys():
    print 'Key:', k
    val = piratelibs[k]
    print 'Value:', val