Variables and operators¶

Class 01¶

Author: Fernando Ferraz Ribeiro¶

1. Python Console and Mathematical Operators¶

After installation, it is possible to run the IDLE PYthon GUI (CPython) or Spyder (Anaconda) program and interact with the Python Shell or Ipython console. You can perform mathematical operations on the shell. Enter 2 + 5 and press the enter key to get the result

In [12]:

2+5

Out[12]:

7

Real numbers must be typed with dots by separating the entire and decimal parts.

In [13]:

2.5 + 5.3

Out[13]:

7.8

Subtraction operations can be performed in a similar manner:

In [14]:

5-2

Out[14]:

3

In [15]:

2-5

Out[15]:

-3

The multiplication operator is the asterisk character.

In [16]:

2*3

Out[16]:

6

In [17]:

5*7

Out[17]:

35

The power (or exponent) of a number is inputed as two asterisks

In [18]:

2**3

Out[18]:

8

In [19]:

3**2

Out[19]:

9

Division:¶

The operator / is responsible for the actual division

In [20]:

4/2

Out[20]:

2.0

In [21]:

5/2

Out[21]:

2.5

Two bars in a row // operate as an entire division. The entire division defines that $5/2$ would have resulted in $= 2$ and the rest $= $1$. The rest of the division can be calculated by the $\%$ operator.

In [22]:

5//2

Out[22]:

2

In [23]:

5%2

Out[23]:

1

The entire division can be done in whole variables and floating point variables.

In [24]:

5%2

Out[24]:

1

In [25]:

5.0//2.0

Out[25]:

2.0

In [26]:

5.0 % 2.0

Out[26]:

1.0

2. Parêmesis levels¶

You can combine several mathematical operations into an expression in Python:

In [27]:

2+3/2

Out[27]:

3.5

You must look at which operation you want to perform:

$\frac{2+3}{2}$

or

$2+\frac{3}{2}$.

The line typed above returns the second option. if the goal is the first it is necessary to use parentheses for the addition operation to be performed first:

In [28]:

(2+3)/2

Out[28]:

2.5

A particularly interesting case occurs in the potentiating of negative numbers. The expression typed below corresnponede at $-\sqrt{2}$.

In [29]:

-2**.5

Out[29]:

-1.4142135623730951

To perform the $\sqrt{-2}$ operation you must type as it appears below.

In [30]:

(-2)**.5

Out[30]:

(8.659560562354934e-17+1.4142135623730951j)

Python 3 returns a complex variable for this oprenation.

3. Variables¶

values can be saved in computer memory for use in later operations. To access these values, you must assign a name to a variable. In Python, to use a smallpox just atrubuir a value to a variable name through the operator $=$.

In [31]:

a = 2
a

Out[31]:

2

In [32]:

b = 2+3
b

Out[32]:

5

3.1 Variable types¶

3.1.1 Boolean¶

In [33]:

a = True
a

Out[33]:

True

In [34]:

b = False
b

Out[34]:

False

In [35]:

type(a)

Out[35]:

bool

In [36]:

type(b)

Out[36]:

bool

3.1.2 Integers¶

In [37]:

a = 2+3
a

Out[37]:

5

In [38]:

type(a)

Out[38]:

int

4.1.3 Floats¶

In [39]:

b = 3.0
b

Out[39]:

3.0

In [40]:

type(b)

Out[40]:

float

In [41]:

c = a+b
c

Out[41]:

8.0

In [42]:

type(c)

Out[42]:

float

3.1.4 Strings¶

In [43]:

c = "hello world"
c

Out[43]:

'hello world'

In [44]:

type(c)

Out[44]:

str

4. Logic operations¶

Not

In [45]:

vLogic = True

not vLogic

Out[45]:

False

In [46]:

vlogic = False

not vlogic

Out[46]:

True

AND

a	b	and
True	True	True
False	True	False
True	False	False
False	False	False

In [47]:

True and True

Out[47]:

True

In [48]:

False and True

Out[48]:

False

In [49]:

True and False

Out[49]:

False

In [50]:

False and False

Out[50]:

False

OR

a	b	or
True	True	True
False	True	True
True	False	True
False	False	False

In [51]:

True or True

Out[51]:

True

In [52]:

False or True

Out[52]:

True

In [53]:

True or False

Out[53]:

True

In [54]:

False or False

Out[54]:

False

Equality

In [55]:

a == a

Out[55]:

True

In [56]:

a == b

Out[56]:

False

Inequality

In [57]:

a != a

Out[57]:

False

In [58]:

a != b

Out[58]:

True

Bigger than (>) smaller than (<)

In [59]:

a

Out[59]:

5

In [60]:

b

Out[60]:

3.0

In [61]:

a < b

Out[61]:

False

In [62]:

a > b

Out[62]:

True

In [63]:

a < a

Out[63]:

False

In [64]:

b < b

Out[64]:

False

Bigger or equal (>=) smaller o equal (<=)

In [65]:

a <= a

Out[65]:

True

In [66]:

a <= 5.0

Out[66]:

True

5.Logic onditions¶

    if

    else

    elif

In [67]:

var1 = 12

In [68]:

if var1 % 2 == 0:
    print(var1, " Even")
else:
    print(var1, " Odds")

12  Even

In [69]:

var2 = 7

In [70]:

if var1 % 2 == 0:
    print(var1, " Even")
else:
    print(var1, " Odds")

12  Even

In [71]:

var3 = 12

In [72]:

if var3 % 2 == 0:
    print (var3, " is divisible by 2")
    if var3 % 3 == 0:
        print (var3, " is divisible by 2 , 3 and 6")
elif var3 % 3 == 0:
    print (var3, " is divisible by 3 and NOT by 2")
    
        
else:
    print (var3, "is NOT divisible by 2 ,  3 nether by 6")

12  is divisible by 2
12  is divisible by 2 , 3 and 6