Getting started with

Python
Comments in Python

• A comment is a line or part of a line that will be ignored by Python.

• A comment in Python begins with one or more # symbols. Everything that follows this symbol
to the end of the line is considered a comment.

You can create a whole line of comments or at the end of a line of code

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Packages in Python

• Python Packages are a way to organize and structure your Python code into reusable components. Think of
it like a folder that contains related Python files (modules) that work together to provide certain
functionality.
• Packages help keep your code organized, make it easier to manage and maintain, and allow you to share
your code with others.
Example :

• NumPy
• Pandas
• SciPy
• Bio

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Packages in Python

• To install a new package: pip install package_name

• Some packages are loaded automatically when you start Python, such as the base subdirectory. To load the
package into memory:

Import package_name

# Use functions or classes from the package

result = package_name.some_function()

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Algorithm, Function and
Variable
Variable
A variable is like a box with a name (or identifier) that contains a value (variable content).
Example:
variable Age, which corresponds to a person's age.
Variable: name = "x" and value = 20 Memory

20
X
Python code:

x = 20
Explanation:
The = operator is called the assignment operator. It takes any value on the right and places it in the variable
indicated on the left. The command might read "put the value 20 in the variable named x".

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Variable
Naming variables in R :

• Allowed characters for variable names are lowercase letters a-z and uppercase letters A-Z, numbers 0-9
and the underscore character "_".
• They may not begin with a number (2x is not valid, but x2 is).
• Python is case-sensitive, meaning foo, Foo and FOO are three distinct variables.
• Certain names are used by the Python system, so it's best to avoid using them. In particular, avoid using
c, q, t, C, D, I, diff, len, mean, pi, range, var. Some words are reserved and may not be used. Words
reserved for the system are: break, else, for, function, if, in, next, repeat, return, while, TRUE, FALSE, Inf,
NA, NaN, NULL, NA_integer_, NA_real_, NA_complex_, NA_character_
• It's also best to avoid dots ( .) in a variable name, as in my.object.
• The name cannot use special symbols such as ^, !, $, @, +, -, /, or *.

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Variable

• Python will overwrite any previous information stored in a variable without asking your permission. It is
therefore advisable not to use names that have already been taken.
• To view variable names already in use, use the environment panel.

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Algorithm
Algorithm => sequence of instructions for solving a problem.

Example: Reconstructing a PUZZLE ( puzzle pieces + followed by instructions / processing + Result )

INPUT ALGORITHM OUTPUT

INPUT FUNCTION OUTPUT

FUNCTION OUTPUT INPUT FUNCTION OUTPUT

INPUT Sub-algorithm

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Function

• Sub-algorithm => division into several smaller parts called FUNCTION.

• A Function is a sequence of instructions grouped under a name. It takes parameters as input (INPUT)
and returns a result (OUTPUT).

INPUT FUNCTION OUTPUT

Argument / parameter

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Function

1. Function declaration 2. Calling or using the Function

• Provide the name of the function • Use the result in a process

• Define the inputs or arguments • Display the result
• Write the processing ( which will use these • Put the result in a variable
arguments to give a result)
• Return the result found
Syntaxe en Python:
Syntaxe en python : Function_name(arg1, arg2, arg3)

def function_name(arg_1, arg_2, arg_3) :

# instructions
return

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Function

Example: Example: Function for calculating the square of a number.

1. Define the arguments or inputs

2. Write the processing
3. Return the result
Output :
Input :Nbr Nbr * Nbr Result of
multiplication

def carre (x):

return x*x

carre(2)

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