Basics of Programming with Python

Basics of Programming with Python#

of

  • Syntax

  • Order of execution

  • Variables

  • Data types

Syntax#

In Python, every line is a new statement. It’s not possible to have multiple statements in one line.

print('(Un)Creative ')
print('Coding ')
print('with Python')

(Un)Creative 
Coding 
with Python

print('(Un)Creative ') print('Coding ') print('with Python')

  Cell In[8], line 1
    print('(Un)Creative ') print('Coding ') print('with Python')
                           ^
SyntaxError: invalid syntax

When writing code, we’ll often receive an SyntaxError, meaning that the code is not executable.

The ^ indicates the position of the error.

Order of execution#

The code is executed from top to bottom. Later we’ll see that it’s possible (and common) to write code that’s less linear.

Variables#

A very powerful concept in programming is the variable. We can store data in variables and use it multiple times through the program, but also change it during the process of execution.

Variables are created through a name of your choice followed by = followed by the data you want to store in it. Allowed characters for variable names: characters, numbers, ‘_’ (underscore). It’s not allowed to start a name with a number. In Python it’s convention to write regular variables in lowercase characters and separate them with _.

s1 = '(Un)Creative' 
s2 = 'Coding' 
s3 = 'with Python'

print(s1, s2, s3)
print(s2, s3)
print(s1)

(Un)Creative Coding with Python
Coding with Python
(Un)Creative

The data inside variables is not fixed. We can override or modify it.

a = 7
print(a)
a = a * 2
print(a)
a *= 2
print(a)
a /= 2 
print(a)
b = 4
a += b 
print(a)

7
14
28
14.0
18.0

Data types#

We’ve got in touch with 3 different types of data already:

  • String (text)

  • Integer (whole numbers)

  • Float (floating point numbers)

We can check the type of data with the function type().

# String
s = 'Some text.'
print(type(s))

# Integer
n1 = 58626
print(type(n1))

# Float
n2 = -25.66
print(type(n2))

<class 'str'>
<class 'int'>
<class 'float'>

Variables do not need to be created with a specific data type (as in some other programming languages). It’s also possible to change the type (it’s done automatically) according to the data we put into it.

a = 'Some text' 
a = 4
a = 0.2

Converting data types (casting)#

It’s easy to convert data into a specific type with built-in methods. This is called casting.

str(4.2)

'4.2'

str(5)

'5'

int('7')

7

int(7.4)

7

float('7')

7.0

float(4)

4.0
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