Expressions

Definition: An expression is an construct of symbols that the python interpreter can evaluate. The expression we can type in the inpreter, and that the interpreter can evaluate meaningfully are

numerical expressions
textual expressions
logical expressions

Numerical Expression



In [1]:

    
x = 5; y = 700; z = 821



In [2]:

    
x + y
x * y
x ** y

# etc.









    Out[2]:





1901091566295159823515072405835103109264871206373519032441746057565854249277472203557201497052621863202610629503298188674778262443788623503544624583852527978187847081031734592912357695384795280342176118255040207774382160198963856151525515423826657984269000422536358621400702420807052018353350982292716419484982535110142249297056924906488555403892140062791926661918530613262656492971667990518503399759909868494802563030058676203176091173708076110583121975938780678916373290121555328369140625L

Textual Expression

The simplest "textual expression" is a string, i.e., a sequence of characters (i.e., alphanumeric symbols, plus puntuation marks, plus special escape sequences).

To let python Know that your text is a string, and not the name of a variable, you need to use quotes:

single quotes: '
double quotes: "
triple quotes: """



In [3]:

    
"Once upon a time\nthere was a little rabbit\nwho liked carrots two much."









    Out[3]:





'Once upon a time\nthere was a little rabbit\nwho liked carrots two much.'



In [4]:

    
"""Once upon a time
there was a little rabbit
who liked carrots two much
He said
I'd live another carrot"""









    Out[4]:





"Once upon a time\nthere was a little rabbit\nwho liked carrots two much\nHe said\nI'd live another carrot"

Operations on strings



In [8]:

    
x = "Benoit"
y = "Dherin"

z = x + ' ' + y
print z









    



Benoit Dherin



In [12]:

    
x = "Hello "
8*x









    Out[12]:





'Hello Hello Hello Hello Hello Hello Hello Hello '

String formatting



In [25]:

    
name = 'Bob'; age = 32; job ='Teacher'; teeth = 12.5
name2 = 'Marcelluscatapultus'; age2 = 3320; job2 ='Yogi'; teeth2 = 122.82



In [26]:

    
print name + job + str(age) + str(teeth)









    



BobTeacher3212.5



In [41]:

    
formatted_string  = "| %-20s | %-20s | %-4d | %-8.2f |" % (name, job, age, teeth)
formatted_string2 = "| %-20s | %-20s | %-4d | %-8.2f |" % (name2, job2, age2, teeth2)

print '_'* 65
print formatted_string
print formatted_string2
print '_'* 65









    



_________________________________________________________________
| Bob                  | Teacher              | 32   | 12.50    |
| Marcelluscatapultus  | Yogi                 | 3320 | 122.82   |
_________________________________________________________________

Logical Expression



In [ ]:



In [6]:

    
True









    Out[6]:





True



In [7]:

    
False









    Out[7]:





False



In [20]:

    
x = True; y = False



In [23]:

    
x and y









    Out[23]:





False



In [24]:

    
x or y









    Out[24]:





True



In [25]:

    
not x









    Out[25]:





False



In [26]:

    
(x or y) and not x









    Out[26]:





False



In [ ]: