Python basics
Advantage of Python
- Interpreter: no need to compile, directly executed.
- Easy: grammar in Python is easy.
- Libraries: a lot of libraries are available.
- Dynamic typing: no need to define the type of variables, functions, etc.
Interactive mode and script mode
- In Python, you can use interactive mode and script mode.
- In the interactive mode, you execute the Python program with the console and write the command to that console.
- In the script mode, you write some file (e.g. test.py) and execute the file from the console like
python test.py
- In the following, we recommend executing commands in the interactive mode. That is, do
pythonin the terminal then execute the command after `>>>``.
The difference between C++ and Python
- C++: compiled, statically typed, and requires manual memory management, providing high performance and control, suited for performance-critical applications.
- Python is interpreted, dynamically typed, and has automatic memory management, prioritizing simplicity, versatility, and rapid development over raw performance.
Variables and types
- In Python, you have the following variable types.
| types | meaning | example |
|---|---|---|
| int | integer | 1, 2, 3 |
| float | floating point number | 1.2, 1.3e10, 1.4e-10 |
| str | string | "hello world" |
| bool | boolian logical variable | True, False |
| complex | complex number | (1, 2) (=1 + 2j) |
So let's define some variables and print them with
printfunction.a = 123 b = 1.2 c = "hello" print(a) print(b) print(c)- You can define variables in one line, as
a, b = 1, 2 print(a) print(b)
comment
- You can put comments, by starting
#. This is a single line comment. Comments with multiple lines can be defined by sandwitching with
""".# this is a comment. """ This part is a comment """
operator
- There are several operators in Python.
| symbol | meaning | example | |||
|---|---|---|---|---|---|
| Arithmetic operators | - | - | |||
| + | add | 1 + 2, "hello" + "world" | |||
| - | subtract | 2 - 1 | |||
| * | multiplicate | 10 * 10 | |||
| ** | power | 10 ** 2 (becomes 100) | |||
| / | divide | 10/2 | |||
| // | floor division (truncation) | 10//3 (becomes 3, not 3.3) | |||
| % | modulus | 10/3 | |||
| Comparison operators | - | - | |||
| == | identical | a == 1 (returns True or False) | |||
| greater than | a > 1 | ||||
| less than | a < 1 | ||||
| = | greater than or equal | a >= 1 | |||
| = | less than or equal | a <= 1 | |||
| Logical operators | - | - | |||
| and | logical and | a == 1 and b == 2 | |||
| or | logical or | a == 1 or b == 2 | |||
| not | logical not | not a == 1 (returns True or False) | |||
| Assignment operators | - | - | |||
| += | replace after addition | a += 1 means a = a + 1 | |||
| -= | replace after subtract | a -= 1 means a = a - 1 | |||
| *= | replace after multiplication | a = 2 means a = a 2 | |||
| /= | replace after division | a /= 2 means a = a / 2 | |||
| %= | replace after modulus | a %= 2 means a = a % 2 | |||
| **= | replace after power | a = 2 means a = a 2 | |||
| //= | replace after floor | a //= 2 means a = a // 2 | |||
| &= | replace after logical and | a &= 2 means a = a & 2 | |||
| = | replace after logical or | a | = 2 means a = a | 2 | |
| Others | - | - | |||
| in | membership operator | a in ["a", "b", "c"] | |||
| is | identity operator | a is 1 |
a = 1
b = 2
c = a + b
d = "Hello "
e = "World"
print(c)
print(a == b)
print(d + e)
Exercise
- Create two variables x and y and assign integer values to them.
- Perform arithmetic operations (addition, subtraction, multiplication, division) using these variables.
- Print the results of each operation. answer