## Chapter 10 — The else branch sends nothing ### Lesson map Lesson 10. Map, example, EX056. ```mermaid flowchart TD E["else assigns a string"] --> P["print writes the line"] P --> N["No socket, no DNS, no packet"] N --> K["Two lines use that else"] ``` The `else` is live code. Its only effect is a line of text. ### Logical drawing ```text imports ipaddress only calls that are absent socket, DNS, connect else runs for 192.0.2.130 198.51.100.7 ``` ### Learning outcomes After this chapter, you should be able to: 1. Name the only import. 2. Say which two lines come from the `else`. 3. Refuse a claim that the script probed those addresses. ### 10.1 A verdict string is not a packet. The file imports `ipaddress` and nothing else. `ip_address` and `ip_network` parse text into objects in memory. The `else` stores the words `OUT OF SCOPE - do not test` and the `print` writes them. There is no socket, no name lookup, and no connection. The comment at the top says no network traffic is sent. The branch structure agrees with that comment: every path ends at `print`. Two of the four lines take the `else`. That means the branch is used. It is not a leftover. Using it still does not contact `192.0.2.130` or `198.51.100.7`. A later reader who "finishes the lab" by reaching those addresses has left the file. | Path | Lines that take it | Leaves the machine? | |---|---|---| | `if` excluded | The payroll line | No | | `elif` in network | The `.5` line | No | | `else` | `.130` and `198.51.100.7` | No | ### 10.2 Worked example | Offered claim | What the file contains | Decision | |---|---|---| | "The miss lines are local prints." | `print` of a string | Keep | | "The else is dead, so those rows were typed by hand." | Two inputs take it | Refuse | | "Out of scope means the script checked the host and found it down." | No such check | Refuse | > **Synthetic case.** The classroom pack never leaves the interpreter. ### Errors and limits Do not add a network call so the refusal "really" checks a host. ### Apply - **EX056 — No packet.** Which import does the scope script use, which lines take the `else`, and does that branch contact a host? *Rubric:* 3 = `ipaddress` only; `.130` and `198.51.100.7` take the `else`; the branch prints and does not contact a host;; 2 = the miss lines are prints and no packet is sent;; 1 = one fact;; 0 = none. ### Continue studying — lesson 10 (chapter 10 of 20) [← Chapter 09](#ch-09) · [Course chapter index](../SUBJECTS.md) · [Chapter 11 →](#ch-11) Continue to the next authored lesson. ## Worked answers **EX056.** The only import is `ipaddress`. The `else` covers `192.0.2.130` and `198.51.100.7`. That branch prints and does not contact a host.