Master Python Basics: Encoding, Keywords, Variables, and Control Flow Explained

1. Encoding

By default, Python 3 source files use UTF-8 encoding and all strings are Unicode. You can specify a different encoding by adding a coding comment at the top of the file.

2. Keywords

Python’s reserved words can be listed using the keyword module, which prints all keywords for the current version.

3. Comments

Single‑line comments start with #. Multi‑line comments are enclosed by three single quotes (''' … ''') or three double quotes (""" … """).

4. Variables

Variables do not need explicit declaration; they are created upon first assignment. Python 3 supports int, float, bool, and complex. Multiple assignment is possible, e.g., a, b = 1, 2. A variable can be reassigned to objects of different types. Division (/) always returns a float; integer division uses //. Mixed arithmetic automatically promotes integers to floats.

5. Strings

Strings are enclosed in single or double quotes; special characters are escaped with a backslash. Concatenation uses +, repetition uses *. Triple quotes ('''…''' or """…"") create multi‑line strings. Prefixing with r makes a raw string where backslashes are not escaped. Indexing starts at 0 from the left and -1 from the right; there is no separate character type—single‑character strings serve that purpose. Strings are immutable; assigning to an index raises an error. Slicing uses obj[start:stop] with a half‑open interval, and either index may be omitted.

6. Ternary Operator

7. Branches

The if‑else statement works like in other languages. The if‑elif‑else chain corresponds to if‑else if‑else in C/Java.

8. Loops

while

loops repeat while a condition is true:

while condition:
    statements

for

loops iterate over a sequence and may include an else clause that runs after normal termination (but not after a break).

To iterate over numbers, use the built‑in range() function, often combined with for loops.