Python Class NYU Lecture Two

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# Python Class Lecture Notes & Tests
# 2014-02-12 Wed
# Numbers and Strings
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#!/user/bin/python

intvar1 = 5
intvar2 = 4
intvar3 = intvar1 / intvar2
print intvar3

print intvar1 / float(intvar2)

### Strings

# if you have a string that contains one type of quotes, you can use the other type to enclose them:

print "I wanted to tell him 'use the one you want'."

#Otherwise, you can escape any quotes if within same-type quotes:
print "I wanted to tell him \"use the one you 'want'\"."

varhello = '''
   hello there
   i am a string with
   some new lines
   '''

print varhello

# When combining object values with strings (i.e., printing them together), it's useful to use string formatting:
name = 'Jose'
value = 54
print '%s is %s years old' % (name, value)      # %s is a token in the string to print, and the (name, value) is a tuple
												# The 'template' is the string, which contains %s tokens.  This string is followed by a % sign and a tuple of values to be inserted.  The number of tuple elements and tokens must match.

alpha = 'abcdefghijklmnop'
print alpha[4:6]
print alpha[7:15]

min = 0
max = 4
print alpha[min:max]

# Strings are sequences of characters, and as such they can be sliced by index:  
mystr = '2359:4323:4444:1112'
first_value = mystr[0:4]      # slice and return first 4 letters
print first_value             # '2359'

# str.split() and str.join(): string->list, list->string
# Here is our first method that returns a list:

mystr = '234:432234:23:9:14'
elements = mystr.split(':')
print elements                # ['234', '432234', '23', '9', '14']

# split is called on a string object, takes a substring as an argument, and splits the string on the substring, dividing it into individual string objects.  
# The substring is removed and does not appear in the string elements.

# join is called on the joining character:
element_list = ['234', '432234', '23', '9', '14']

mystr = ':'.join(element_list)
print mystr                   # 234:432234:23:9:14

mystr = '\n'.join(element_list)
print mystr                   # prints the numbers on a separate line

# print is actually a convenience function - it outputs strings to the screen, but it also adds a newline to the end:
print 'hey'        # prints 'hey\n'
print 'there'      # prints 'there\n'

# if we want to omit the newline, we can add a comma to the end - now a space is added:
print 'hey', 
print 'there'      # prints 'hey there'

# if we want to avoid anything being added to our strings we can use sys.stdout.write() -- more on this later:
import sys
sys.stdout.write('hey')
sys.stdout.write('there')     # prints 'heythere'
print

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