Python Environment Setup

Download the Python interpreter from the official website: https://www.python.org/downloads/

For development, PyCharm IDE can be activated using verification codes from http://idea.lanyus.com/

Script Header Configuration

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Author: Example
# Description: Multi-function script
# Created: 2018-08-13
# Execution: python script_name.py

Linux Package Manager Configuration

Configure pip source on Linux by creating or modifying ~/.pip/pip.conf:

[global]
timeout = 6000
index-url = http://pypi.douban.com/simple
trusted-host = pypi.douban.com

Python Script Execution Methods

Execute Python scripts using the Python interpreter directly. Python files can have any extension.

Character Encoding Systems

• ASCII: 8-bit character encoding
• Unicode: 16-bit universal character set
• UTF-8: Variable-length Unicode compression
• GBK: Chinese character encoding standard

Example: The Chinese characters "李杰" occupy 6 bytes in UTF-8 and 4 bytes in GBK encoding.

Comments

Single-line: # Comment text Multi-line: """Comment text"""

Variable Declaration and Usage

#!/usr/bin/env python
# -*- coding: utf-8 -*-

username = 'admin'    # Variable assignment
username               # Variable reference
print(username)        # Print variable value

Variable Naming Rules

• Variable names can contain letters, numbers, and underscores
• Cannot start with a number
• Avoid Python keywords: ['and', 'as', 'assert', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'exec', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'not', 'or', 'pass', 'print', 'raise', 'return', 'try', 'while', 'with', 'yield']
• Use meaningful names
• Case-sensitive
• Recommended naming conventions: camelCase or snake_case

Basic Input/Output

# Simple input/output
user_input = input('Enter username: ')
pass_input = input('Enter password: ')
print(user_input, pass_input)

# Secure password input
import getpass

user_id = input('Username: ')
secure_pass = getpass.getpass('Password: ')
print(user_id, secure_pass)

# Authentication example
import getpass

stored_user = 'alex'
stored_pass = 'as123'

input_user = input('Username: ')
input_pass = input('Password: ')

if stored_user == input_user and stored_pass == input_pass:
    print(f'Welcome {stored_user}!')
else:
    print('Invalid credentials')

Loop Structures

For Loops

# Basic range iteration
for counter in range(10):
    print('Iteration', counter)

# Range with parameters
for index in range(0, 10, 3):
    print('Step', index)

# Continue statement
for value in range(10):
    if value < 3:
        print('Value:', value)
    else:
        print('Skipping...')
        continue
    print('Processing...')

# Nested loops with break
for outer in range(9):
    print('Outer:', outer)
    for inner in range(11, 50):
        print('Inner:', inner)
        if inner >= 22:
            break

Data Types

Numeric Types

• int: Integer values (-9223372036854775808 to 9223372036854775807)
• float: Floating-point numbers (e.g., 3.23, 52.3E-4)
• complex: Complex numbers (e.g., -5+4j)

Boolean Values

• True or False (1 or 0)

Strings

Text sequences: "hello world"

Type Conversion Functions

• int(x[, base]): Convert to decimal integer
• float(x): Convert to floating-point
• str(object): Convert to string
• tuple(seq): Convert sequence to tuple
• list(seq): Convert sequance to list
• chr(x): Integer to character
• ord(x): Character to integer value
• hex(x): Integer to hexadecimal string
• oct(x): Integer to octal string

Operators

Arithmetic Operators

+   # Addition
-   # Subtraction
*   # Multiplication
/   # Division
%   # Modulus
**  # Exponentiation
//  # Floor division

Comparison Operators

==  # Equal
!=  # Not equal
>   # Greater than
<   # Less than
>=  # Greater than or equal
<=  # Less than or equal

Logical Operators

and  # Logical AND
or   # Logical OR
not  # Logical NOT

Bitwise Operators

&   # Bitwise AND
|   # Bitwise OR
^   # Bitwise XOR
~   # Bitwise NOT
<<  # Left shift
>>  # Right shift

Operater Precedence

1. ** Exponentiation
2. ~, +, - (unary)
3. *, /, %, //
4. +, - (binary)
5. <<, >>
6. &
7. ^, |
8. Comparison operators
9. Assignment operators
10. Identity operators
11. Membership operators
12. Logical operators

Ternary Operator

result = value1 if condition else value2

Number Systems

• Binary: Base-2 (0-1)
• Octal: Base-8 (0-7)
• Decimal: Base-10 (0-9)
• Hexadecimal: Base-16 (0-9, A-F)

Programmming Exercises

Print Numbers 1-10 (Skip 7)

counter = 1
while counter < 11:
    if counter != 7:
        print(counter)
    counter += 1

Sum of 1-100

total = 0
number = 1
while number < 101:
    total += number
    number += 1
print(total)

Even Numbers 1-100

value = 1
while value < 101:
    if value % 2 == 0:
        print(value)
    value += 1

Alternating Sum 1-99

current = 1
result = 0
while current < 100:
    if current % 2 == 0:
        result -= current
    else:
        result += current
    current += 1
print(result)

Login System with Retry

import getpass

correct_user = "zhao"
correct_pass = "123456"
attempts = 0

while attempts < 3:
    input_user = input("Enter username: ")
    input_pass = input("Enter password: ")
    
    if input_user == correct_user and input_pass == correct_pass:
        print("Access granted")
        break
    elif not input_user or not input_pass:
        print("Fields cannot be empty")
        attempts += 1
    else:
        print("Invalid credentials")
        attempts += 1

Control Structures

Conditional Statements

# Basic if statement
value = 5
if value > 2:
    print('Condition met')

# If-else structure
if value > 8:
    print('High value')
else:
    print('Low value')

# If-elif-else chain
if value > 8:
    print('High')
elif value > 3:
    print('Medium')
else:
    print('Low')

For Loop Examples

# Iterate through range
for i in range(5):
    print(i)

# List iteration
names = ['Michael', 'Bob', 'Tracy']
for name in names:
    print(name)

# Sum calculation
sum_total = 0
for x in range(101):
    sum_total += x
print(sum_total)

Chicken Problem Solution

for roosters in range(1, 20):
    for hens in range(1, 33):
        chicks = 100 - roosters - hens
        if (chicks % 3 == 0) and (roosters * 5 + hens * 3 + chicks / 3 == 100):
            print(f"Roosters: {roosters}; Hens: {hens}; Chicks: {chicks}")

While Loop with Break/Continue

# Break example
n = 1
while n <= 100:
    if n > 10:
        break
    print(n)
    n += 1

# Continue example
num = 0
while num < 10:
    num += 1
    if num % 2 == 0:
        continue
    print(num)