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kb/python-course-kb-practical-python/wiki/exercises/1-6-debugging.md

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+---
+id: practical-python-1.6
+source_exercise_id: "1.6"
+title: "Debugging"
+section: "1.2 A First Program"
+source_path: "01_Introduction/02_Hello_world.md"
+source_repo: "https://github.com/dabeaz-course/practical-python"
+source_commit: "93dca856b41c61a0a0f85ae334116e4c125629ea"
+student_visible_solution: false
+has_private_solution: false
+skip: false
+---
+
+# Exercise 1.6: Debugging
+
+> Source: Practical Python Programming, `01_Introduction/02_Hello_world.md`.
+
+### Exercise 1.6: Debugging
+
+The following code fragment contains code from the Sears tower problem.  It also has a bug in it.
+
+```python
+# sears.py
+
+bill_thickness = 0.11 * 0.001    # Meters (0.11 mm)
+sears_height   = 442             # Height (meters)
+num_bills      = 1
+day            = 1
+
+while num_bills * bill_thickness < sears_height:
+    print(day, num_bills, num_bills * bill_thickness)
+    day = days + 1
+    num_bills = num_bills * 2
+
+print('Number of days', day)
+print('Number of bills', num_bills)
+print('Final height', num_bills * bill_thickness)
+```
+
+Copy and paste the code that appears above in a new program called `sears.py`.
+When you run the code you will get an error message that causes the
+program to crash like this:
+
+```code
+Traceback (most recent call last):
+  File "sears.py", line 10, in <module>
+    day = days + 1
+NameError: name 'days' is not defined
+```
+
+Reading error messages is an important part of Python code. If your program
+crashes, the very last line of the traceback message is the actual reason why the
+the program crashed. Above that, you should see a fragment of source code and then
+an identifying filename and line number.
+
+* Which line is the error?
+* What is the error?
+* Fix the error
+* Run the program successfully
+
+
+[Contents](../Contents.md) \| [Previous (1.1 Python)](01_Python.md) \| [Next (1.3 Numbers)](03_Numbers.md)
+
+## 关联来源
+
+- [[summaries/02_Hello_world]]