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Python Basics

First steps with Python: print, variables, if/else, loop, function. Write 5 short scripts as .py files.

Duration: 30 minLevel: BeginnerExercises: 5

Your first Python scripts

Python basics: your first scripts

Python is one of the most-used programming languages — easy to read and ideal to start with. A script is a text file ending in .py that you run with python3 file.py.

Key terms

print(): outputs something to the screen.
Variable: a named storage slot for a value, e.g. name = "Max".
if/else: makes decisions depending on a condition.
for loop: repeats something for each element.
Function (def): a named, reusable block of code.

Work in the folder /home/student/python/ (mkdir -p /home/student/python). Edit files with nano, run with python3 file.py.

Your goal

You write five small scripts and learn the most important building blocks of any programming language.

Exercises

1. Hello world with print
Concept: print(). The function print() displays text. Write a script that outputs "Hello World".
```
mkdir -p /home/student/python
echo 'print("Hello World")' > /home/student/python/hallo.py
python3 /home/student/python/hallo.py
```
Check: hallo.py contains a print(...) call.
2. Variable + print
Concept: variable. A variable stores a value under a name. Create a variable and print it with print().
```
nano /home/student/python/variable.py
```
Content:
```
name = "Max"
print(name)
```
Check: variable.py contains an assignment (name = ...) and a print(name).
3. A decision with if/else
Concept: if/else. With if you test a condition; else is the case when it does not hold. Important: the code inside if/else is indented (4 spaces).

nano /home/student/python/entscheidung.py:
```
age = 16
if age >= 18:
    print("adult")
else:
    print("minor")
```
Check: entscheidung.py contains an if ...: with a matching else:.
4. A for loop
Concept: for loop. A for loop repeats a block for each element of a sequence. range(5) produces the numbers 0–4.

nano /home/student/python/schleife.py:
```
for i in range(5):
    print(i)
```
Check: schleife.py contains a for ... in ...: loop.
5. Your own function
Concept: function (def). A function bundles code under a name so you can reuse it. It can take parameters.

nano /home/student/python/funktion.py:
```
def greeting(name):
    print("Hello " + name)

greeting("Max")
```
Check: funktion.py contains a function definition def name(parameter):.

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Your first Python scripts

Python basics: your first scripts

Key terms

Your goal

Exercises

1. Hello world with print

2. Variable + print

3. A decision with if/else

4. A for loop

5. Your own function

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Now practice it yourself