Variables and the types you'll actually use

A variable is a named box that holds a value. You make one by assigning with =. Python figures out the type for you — you never have to declare it. That’s the whole concept, and you’ll use it in every line of code you ever write.

The five types that matter

You don’t need to memorise a long list. Five types carry almost all of security scripting:

target = "example.com"      # str   — a string (text)
port = 443                  # int   — a whole number
ratio = 1.5                 # float — a decimal number
is_up = True                # bool  — True or False
nothing = None              # None  — the "no value" value

print(type(target))         # <class 'str'> — type() tells you what something is

Walk through it. target = "example.com" stores text — the quotes are what make it a string. port = 443 has no quotes, so it’s a number you can do maths with. True and False are booleans (note the capital letters). And None means “nothing here yet” — you’ll see it when a lookup fails or a function returns no result.

The trap that gets everyone

Here’s the one to burn into memory early: the string "443" and the number 443 are not the same thing, and Python treats them differently.

"443" + 1       # CRASHES — you can't add a number to text
443 + 1         # 444     — normal maths
"443" + "1"     # "4431"  — gluing two strings together

When you read a port or an ID out of a file, it arrives as text. If you need to do maths with it, convert it explicitly.

int("443")      # 443  — text to number
str(443)        # "443" — number to text

Choosing good names

Variable names are free — spend them. t = "example.com" saves three keystrokes and costs you clarity every time you reread the code. target = "example.com" tells the next person (usually future-you) exactly what it holds.

# Hard to follow later:
x = requests.get(u).status_code

# Tells the story:
status = requests.get(target_url).status_code

Summary

A variable is a named box; you assign with = and Python infers the type. The five types you’ll lean on are str, int, float, bool, and None. The string "443" and the integer 443 behave differently — convert explicitly with int() and str(). Name variables clearly; the keystrokes you save aren’t worth the confusion they cost.

Key takeaways

• = assigns a value; Python figures out the type.
• Quotes make a string; no quotes makes a number.
• "443" is not 443 — convert with int() / str() when needed.
• Clear, lowercase, underscore names pay you back every time you reread.

Next, we go deep on the type you’ll touch more than any other: strings. Almost everything in security work — URLs, tokens, headers, responses — is text.