PLEASE
REFRESH THIS PAGE TO GET THE LATEST VERSION

number1 = input("Enter first number:\n")

a

see program:

http://www.annedawson.net/python3programs.html

04-01.py

For more notes on Python 3 input, see:

http://www.annedawson.net/Python3_Input.txt

see program:

http://www.annedawson.net/python3programs.html

04-02.py

A representation of the memory location of an object
can be obtained by using the id function.

number1 = input("Enter first
number:\n")

print (number1, type(number1), id(number1))

number1 = int(number1)

print (number1, type(number1) ),
id(number1))

see program:

http://www.annedawson.net/python3programs.html

04-03.py

```
The % (modulus or modulo) operator yields the remainder
from the division of the first argument by the second. The arguments may be
floating point numbers, e.g., 3.14
% 0.7 equals 0.34 (since 3.14
equals 4 * 0.7 + 0.34.),
```

```
or integer numbers, e.g., 5 % 2 equals 1 (since 5 equals 2
* 2 + 1.).
```

** **

**Click
here for info on when you might want to use the modulus operator.**

see program:

http://www.annedawson.net/python3programs.html

04-04.py

see program:

http://www.annedawson.net/python3programs.html

04-05.py

```
The % (modulus or modulo) operator yields the remainder
from the division of the first argument by the second. The arguments may be
floating point numbers, e.g., 3.14
% 0.7 equals 0.34 (since 3.14
equals 4 * 0.7 + 0.34.),
```

```
or integer numbers, e.g., 5 % 2 equals 1 (since 5 equals 2
* 2 + 1.).
```

** **

**Click
here for info on when you might want to use the modulus operator.**

```
The % (modulus or modulo) operator yields the remainder from
the division of the first argument by the second. The arguments may be floating
point numbers, e.g., 3.14 % 0.7 equals 0.34 (since 3.14 equals 4 * 0.7 +
0.34.),
```

```
or integer numbers, e.g., 5 % 2 equals 1 (since 5 equals 2
* 2 + 1.).
```

** **

**Click
here for info on when you might want to use the modulus operator.**

see program:

http://www.annedawson.net/python3programs.html

04-06.py

These are Boolean expressions.

The result of these expressions is either true (1) or
false (0).

see program:

http://www.annedawson.net/python3programs.html

04-07.py

see program:

http://www.annedawson.net/python3programs.html

04-08.py

see program:

http://www.annedawson.net/python3programs.html

04-09.py

**Highest precedence**

** (exponentiation)

**Lowest precedence**

What the
above means is explained in the examples below:

**Example 1**

x = 17 / 2 * 3 + 2

**print (x)**

** **

`In the expression to evaluate the value of x, the operators / and * share equal precedence `

`that is higher than that of the + operator. `

`Hence the division and multiply are done before the addition, `

`resulting in an output of 27.5, as explained here...`

` `

`17 / 2 is 8.5`

`8.5 * 3 is 25.5`

`25.5 + 2 is 27.5`

` `

` `

` `

Example 2

x = 2 + 17 / 2 * 3

**print (x)**

** **

`In the expression to evaluate the value of x, the operators / and * share equal precedence`

`that is higher than that of the + operator. `

`Hence the division and multiply are done before the addition, `

`resulting in an output of 27.5, as explained here...`

** **

`17 / 2 is 8.5`

`8.5 * 3 is 25.5`

`25.5 + 2 is 27.5`

** **

** **

** **

** **

Example 3

` `

```
or integer numbers, e.g., 5 % 2 equals 1 (since 5 equals 2
* 2 + 1.).
```

** **

**Click here for info on when you might want to use the modulus operator.**

** **

**x = 19 % 4 + 15 / 2 * 3**

**print (x)**

** **

`In the expression to evaluate the value of x, the operators % / and * share equal precedence `

`that is higher than that of the + operator. `

`Hence the % (modulus), division and multiply are done before the addition, `

`resulting in an output of 25.5, as explained here...`

** **

`19 % 4 is 3`

`15 / 2 is 7.5`

`7.5 * 3 is 22.5`

`22.5 + 3 is 25.5`

** **

** **

** **

** **

Example 4

** **

**x = (15 + 6) - 10 * 4**

**print (x)**

** **

`In the expression to evaluate the value of x, the brackets have highest of all precedence, `

`so is evaluated before anything else, then * is done, and lastly the - subtraction, `

`resulting in an output of -19 (minus 19), as explained here...`

** **

`15 + 6 is 21`

`10 * 4 is 40`

`21 - 40 is -19`

` `

` `

Example 5

x = 17 / 2 % 2 * 3**3

**print (x)**

** **

`In the expression to evaluate the value of x, the exponentiation is done first `

`(three to the power of 3 is 3 * 3 * 3 which equals 27) as it has higher precedence to the other operators (/ % and *). `

` `

`So, ...`

` `

`This is the order of evaluation:`

`Exponentiation is done first and the expression then evaluates from left to right:`

3 to the power of 3 is 27.

the
expression is now 17 / 2 % 2 * 27

17 / 2 is
8.5

8.5 % 2 is
0.5

0.5 *
27 is 13.5

The if statement starts with the keyword if followed
by a Boolean expression, followed by a colon (:).

Beneath the if line, the
statements to be run if the condition is true are entered after pressing the
Tab key or typing a few space characters. If you use the Tab key, always use the Tab key. If you use three spaces,
always use three spaces. Mixing Tabs and spaces is a syntax error, even if the
program looks correct! You will get an "incorrect indent" error. You
have been warned!

Click here for
more on using spaces and tabs for indenting Python programs.

The if statement makes use of a Boolean
expression to decide which statement(s) to execute.

The Boolean expression in this
example is:

x ==
'spam'

The expression has a value of true or false (1 or 0).

The Boolean expression is also known
as the *condition* of the if statement.

If the condition is *true*,

the first print statement is executed and the second
one is skipped.

If the condition is *false*,

the first print statement is skipped and the second
one is executed.

It's possible to have multiple
statements in the true or false sections

of an if
statement...

If the condition is *true*, the
first two print statements are executed

and the second set are skipped.

The if statement starts with the keyword if followed by
a Boolean expression, followed by a colon (:).

Beneath the if line, the
statements to be run if the condition is true are entered after pressing the
Tab key or typing a few space characters.

The statements to be run *must*
be indented to the same level.

It's recommended to press the Tab
key before typing the statements.

If you use the Tab key, always use the Tab key. If you
use three spaces, always use three spaces. Mixing Tabs and spaces is a syntax
error, even if the program looks correct! You will get an "incorrect
indent" error. You have been warned!

The else part of an if statement
is optional, but if included, must be followed by a colon (:), and
then the indented statement(s) to be executed if the condition is false.

see programs:

http://www.annedawson.net/python3programs.html

04-10.py

04-11.py

04-12.py

Nested if/else statements test for multiple cases

by placing if/else selection structures inside other

if/else selection structures

see programs:

http://www.annedawson.net/python3programs.html

04-13.py

04-14.py

Nested if/else statements can be written using an alternate

if/elif/else construct.

Program 04-14.py is exactly equivalent to 04-15.py.

see program:

http://www.annedawson.net/python3programs.html

04-15.py

04-17.py

(You will
NOT be tested on De Morgan's Laws on this course)

1. A not and is equivalent to an or with two negated inputs.

2. A not or is equivalent to an and with two negated inputs.

see program:

http://www.annedawson.net/python3programs.html

04-16.py

http://www.annedawson.net/python3programs.html

04-01.py

04-02.py

04-03.py

04-04.py

04-05.py

04-06.py

04-07.py

04-08.py

04-09.py

04-10.py

04-11.py

04-12.py

04-13.py

04-14.py

04-15.py

04-16.py

04-17.py