day1_python_network_basics.py

#!/usr/bin/env python3
"""
=============================================================
  60-DAY PYTHON NETWORK AUTOMATION — DAY 1 & 2
  Onyedikachi Onwe | Atlas Kenji Ltd
  Topic: Python Foundations for Network Engineers
=============================================================

WHAT YOU WILL LEARN TODAY:
  - Variables, data types, print
  - Lists and dictionaries (used everywhere in networking)
  - Loops and if/else logic
  - Functions
  - Mini-project: Simple subnet calculator

RUN THIS FILE:
  python3 day1_python_network_basics.py
=============================================================
"""

# ─────────────────────────────────────────────
# SECTION 1: VARIABLES AND DATA TYPES
# ─────────────────────────────────────────────
print("=" * 55)
print("  SECTION 1: Variables and Data Types")
print("=" * 55)

# Strings — device names, IP addresses, hostnames
hostname       = "SW-CORE-01"
ip_address     = "192.168.1.1"
vendor         = "Cisco"

# Integers — port numbers, VLANs, hop counts
vlan_id        = 100
port_number    = 22          # SSH port
max_hops       = 15          # RIP max hop count

# Floats — bandwidth in Gbps, latency in ms
bandwidth_gbps = 1.0
latency_ms     = 2.5

# Booleans — device reachable? interface up?
is_reachable   = True
interface_up   = True

print(f"Hostname    : {hostname}")
print(f"IP Address  : {ip_address}")
print(f"Vendor      : {vendor}")
print(f"VLAN ID     : {vlan_id}")
print(f"SSH Port    : {port_number}")
print(f"Reachable   : {is_reachable}")
print(f"Interface Up: {interface_up}")
print()


# ─────────────────────────────────────────────
# SECTION 2: LISTS — storing multiple devices
# ─────────────────────────────────────────────
print("=" * 55)
print("  SECTION 2: Lists (Device Inventory)")
print("=" * 55)

# A list of switch IPs in your network
switches = [
    "192.168.1.10",
    "192.168.1.11",
    "192.168.1.12",
    "192.168.1.13",
]

routers = [
    "10.0.0.1",
    "10.0.0.2",
]

print(f"Total switches : {len(switches)}")
print(f"First switch   : {switches[0]}")    # index starts at 0
print(f"Last switch    : {switches[-1]}")   # -1 = last item

# Loop through all switches — you'll use this pattern constantly
print("\nAll switches in the network:")
for ip in switches:
    print(f"  -> {ip}")

# Add a new switch
switches.append("192.168.1.14")
print(f"\nAfter adding new switch, total: {len(switches)}")
print()


# ─────────────────────────────────────────────
# SECTION 3: DICTIONARIES — device profiles
# ─────────────────────────────────────────────
print("=" * 55)
print("  SECTION 3: Dictionaries (Device Profiles)")
print("=" * 55)

# A dictionary stores key-value pairs — perfect for device info
# This is the same structure Netmiko uses to connect to devices!
device = {
    "hostname"      : "SW-CORE-01",
    "ip"            : "192.168.1.10",
    "vendor"        : "cisco",
    "model"         : "Catalyst 3750",
    "os_version"    : "IOS 15.2",
    "location"      : "Server Room - Rack A1",
    "port"          : 22,
    "interfaces"    : ["Gi0/1", "Gi0/2", "Gi0/3", "Gi0/4"],
    "is_reachable"  : True,
}

print(f"Device     : {device['hostname']}")
print(f"IP         : {device['ip']}")
print(f"Location   : {device['location']}")
print(f"Interfaces : {device['interfaces']}")

# Update a value
device["os_version"] = "IOS 15.4"
print(f"Updated OS : {device['os_version']}")

# A list of device dictionaries — your first real inventory!
network_inventory = [
    {"hostname": "SW-CORE-01", "ip": "192.168.1.10", "role": "core-switch",    "vendor": "cisco"},
    {"hostname": "SW-ACC-01",  "ip": "192.168.1.11", "role": "access-switch",  "vendor": "cisco"},
    {"hostname": "SW-ACC-02",  "ip": "192.168.1.12", "role": "access-switch",  "vendor": "huawei"},
    {"hostname": "RTR-EDGE-01","ip": "10.0.0.1",     "role": "edge-router",    "vendor": "cisco"},
    {"hostname": "RTR-EDGE-02","ip": "10.0.0.2",     "role": "edge-router",    "vendor": "huawei"},
]

print("\nFull Network Inventory:")
print(f"  {'HOSTNAME':<16} {'IP':<16} {'ROLE':<16} {'VENDOR'}")
print(f"  {'-'*16} {'-'*16} {'-'*16} {'-'*8}")
for d in network_inventory:
    print(f"  {d['hostname']:<16} {d['ip']:<16} {d['role']:<16} {d['vendor']}")
print()


# ─────────────────────────────────────────────
# SECTION 4: IF / ELSE — decision logic
# ─────────────────────────────────────────────
print("=" * 55)
print("  SECTION 4: If / Else (Device Logic)")
print("=" * 55)

def check_device_status(device_info):
    """Check if a device is reachable and print its status."""
    if device_info["is_reachable"]:
        print(f"  [UP]   {device_info['hostname']} ({device_info['ip']}) is online")
    else:
        print(f"  [DOWN] {device_info['hostname']} ({device_info['ip']}) is OFFLINE — alert!")

# Simulate some devices being down
device_statuses = [
    {"hostname": "SW-CORE-01",  "ip": "192.168.1.10", "is_reachable": True},
    {"hostname": "SW-ACC-01",   "ip": "192.168.1.11", "is_reachable": False},
    {"hostname": "SW-ACC-02",   "ip": "192.168.1.12", "is_reachable": True},
    {"hostname": "RTR-EDGE-01", "ip": "10.0.0.1",     "is_reachable": True},
    {"hostname": "RTR-EDGE-02", "ip": "10.0.0.2",     "is_reachable": False},
]

print("Device Status Report:")
offline_count = 0
for d in device_statuses:
    check_device_status(d)
    if not d["is_reachable"]:
        offline_count += 1

print(f"\n  Summary: {offline_count} device(s) offline out of {len(device_statuses)}")
print()


# ─────────────────────────────────────────────
# SECTION 5: FUNCTIONS — reusable code blocks
# ─────────────────────────────────────────────
print("=" * 55)
print("  SECTION 5: Functions")
print("=" * 55)

def get_device_by_role(inventory, role):
    """
    Filter the inventory and return all devices matching a given role.
    This is a pattern you will use constantly in automation scripts.
    """
    matched = []
    for device in inventory:
        if device["role"] == role:
            matched.append(device)
    return matched


def summarise_inventory(inventory):
    """Print a summary count by vendor."""
    vendor_count = {}
    for device in inventory:
        v = device["vendor"]
        if v in vendor_count:
            vendor_count[v] += 1
        else:
            vendor_count[v] = 1
    return vendor_count


# Use the functions
core_switches   = get_device_by_role(network_inventory, "core-switch")
access_switches = get_device_by_role(network_inventory, "access-switch")
edge_routers    = get_device_by_role(network_inventory, "edge-router")

print(f"Core switches   : {len(core_switches)}")
print(f"Access switches : {len(access_switches)}")
print(f"Edge routers    : {len(edge_routers)}")

vendor_summary = summarise_inventory(network_inventory)
print("\nDevices by vendor:")
for vendor, count in vendor_summary.items():
    print(f"  {vendor:<10} : {count} device(s)")
print()


# ─────────────────────────────────────────────
# MINI-PROJECT: SUBNET CALCULATOR
# (Using Python's built-in ipaddress module)
# ─────────────────────────────────────────────
print("=" * 55)
print("  MINI-PROJECT: Subnet Calculator")
print("=" * 55)

import ipaddress   # built-in Python library — no install needed!

def subnet_info(cidr):
    """
    Take a CIDR notation like '192.168.1.0/24'
    and print full subnet details — useful for planning & docs.
    """
    network = ipaddress.IPv4Network(cidr, strict=False)

    print(f"\n  Network     : {network.network_address}")
    print(f"  Subnet Mask : {network.netmask}")
    print(f"  Broadcast   : {network.broadcast_address}")
    print(f"  CIDR        : /{network.prefixlen}")
    print(f"  Total IPs   : {network.num_addresses}")
    print(f"  Usable Hosts: {network.num_addresses - 2}")
    print(f"  First Host  : {list(network.hosts())[0]}")
    print(f"  Last Host   : {list(network.hosts())[-1]}")


def is_ip_in_network(ip, cidr):
    """Check if a given IP belongs to a subnet."""
    network = ipaddress.IPv4Network(cidr, strict=False)
    addr    = ipaddress.IPv4Address(ip)
    return addr in network


# Test the calculator
print("\n--- Office LAN ---")
subnet_info("192.168.1.0/24")

print("\n--- Management VLAN ---")
subnet_info("10.0.0.0/29")   # small /29 — only 6 usable hosts

print("\n--- IP Membership Check ---")
test_cases = [
    ("192.168.1.50",  "192.168.1.0/24"),
    ("192.168.2.1",   "192.168.1.0/24"),
    ("10.0.0.5",      "10.0.0.0/29"),
    ("10.0.0.10",     "10.0.0.0/29"),
]
for ip, net in test_cases:
    result = "YES — in subnet" if is_ip_in_network(ip, net) else "NO  — not in subnet"
    print(f"  {ip:<16} in {net:<20} -> {result}")


# ─────────────────────────────────────────────
# WHAT'S NEXT — DAY 3 & 4 PREVIEW
# ─────────────────────────────────────────────
print()
print("=" * 55)
print("  DAY 1-2 COMPLETE!")
print("=" * 55)
print("""
  You now know:
    [x] Variables, strings, integers, booleans
    [x] Lists — storing multiple device IPs
    [x] Dictionaries — device profiles (Netmiko format!)
    [x] Loops — iterating over all devices
    [x] If/else — status checking logic
    [x] Functions — reusable automation blocks
    [x] ipaddress module — subnet calculations

  DAY 3-4 CHALLENGE — try these yourself:
  ─────────────────────────────────────────
  1. Add 3 more devices to network_inventory
     with a new role called "firewall"

  2. Write a function called get_cisco_devices()
     that returns only Cisco devices from the inventory

  3. Use subnet_info() to calculate info for:
     172.16.0.0/20  (a medium enterprise subnet)

  4. Write a function that checks if two IP addresses
     are on the same subnet
     Hint: use is_ip_in_network() as a starting point

  COMING DAY 5-6:
    - Reading/writing files (CSV device inventory)
    - Parsing real config output from routers
    - Saving your subnet reports to a .txt file

  Keep going, Onyedikachi. Every line you write
  today is a step toward that remote role.
""")