Running Python Scripts

To execute a Python script, navigate to the file's directory in the command line and run:

python script_name.py

Alternatively, use the terminal in your development environment.

Basic Data Types

Identifiers

Identifiers are user-defined names for variables, functions, and classes.

• Composed of letters, digits, underscores, or dollar signs
• Cannot start with a digit
• Cannot contain spaces

Naming conventions:

• camelCase: variables and functions (e.g., myVariable)
• PascalCase: classes (e.g., MyClass)
• snake_case: underscores between words (e.g., my_variable)

Keywords

Reserved words in Python that cannot be used as identifiers:

import keyword
print(keyword.kwlist)

Comments

Single-line comments start with #. Multiline comments use triple quotes:

# Single-line comment

"""
Multiline
comment
"""

Constants

Constants are immutable values:

• Integers: 10 (decimal), 0b1010 (binary), 0o12 (octal), 0xA (hexadecimal)
• Floats: 3.14, 1.2e3
• Strings: "Hello" or 'World'
• Booleans: True, False
• Complex numbers: 3+4j or complex(3,4)

Variables

Variables store references to data objects:

value = 10
x, y, z = 1, 2, 3
a = b = c = 5

Type Conversion

int_value = int(3.14)        # 3
float_val = float(10)        # 10.0
str_val = str(123)           # '123'
bool_val = bool("text")      # True
bin_str = bin(10)            # '0b1010'
oct_str = oct(10)            # '0o12'
hex_str = hex(10)            # '0xa'
char_code = ord('A')         # 65
character = chr(66)          # 'B'

Mathematical Functions

absolute = abs(-5)           # 5
power = pow(2, 3)            # 8
maximum = max(1, 5, 2)       # 5
rounded = round(3.14159, 2)  # 3.14

Input and Output

user_input = input("Enter a number: ")
number = eval(user_input)
print("Result:", number + 1)

name = "Alice"
age = 25
print(f"{name} is {age} years old.")

Operators

Arithmetic

sum = 5 + 3       # 8
diff = 10 - 4     # 6
product = 7 * 2   # 14
quotient = 10 / 3 # 3.333...
floor_div = 10 // 3 # 3
remainder = 10 % 3 # 1
exponent = 2 ** 4 # 16

Comparison

equals = (5 == 5)        # True
not_equal = (5 != 3)     # True
greater = (10 > 5)       # True
chained = (1 < 2 < 3)    # True

Logical

and_result = (True and False)  # False
or_result = (True or False)    # True
not_result = not True          # False

Bitwise

bit_and = 13 & 7    # 5
bit_or = 13 | 7     # 15
right_shift = 16 >> 2 # 4
left_shift = 2 << 3   # 16
bit_xor = 13 ^ 7     # 10

Membership and Identity

in_list = 3 in [1,2,3]         # True
is_same = (1000 is 1000)       # False (different objects)
equals_val = (1000 == 1000)    # True (same value)

Conditional Statements

if condition:
    # execute if true
elif other_condition:
    # execute if previous false and this true
else:
    # execute if all false

Loop Structures

for i in range(5):
    print(i)

for char in "Hello":
    print(char)

count = 0
while count < 5:
    print(count)
    count += 1

Sequences and Indexing

items = ['a', 'b', 'c', 'd']
first = items[0]    # 'a'
last = items[-1]    # 'd'