1. LING 388: Computers and Language
Lecture 8

2. Administrivia Next week I'm out of town
The TA Patricia Lee will lead both classes
You will do Python programming exercises in class

3. Python numbers revisited
Python invisibly automatically converts to type long int from int (32 bit 2's complement), (page 64–65, section 3.5)
explicit type coercion:
float()
int()
long() Python2.7
complex(r,i)
complex(string)

4. Python numbers revisited
Note the difference in precision here

5. Python numbers revisited
page 60: see factorial.py
Python 3.x
Python 2.7 ( )

6. Python eval()
Think of eval(input()) as being the same as the user typing directly at the Python console …

7. Python numbers revisited
factorial2.py

8. argv[1] and argv[2] ignored
Python argv
List of arguments from the command line: what's argv[0] then?
test.py
argv[1] and argv[2] ignored

9. Python example How about printing to 2 decimal places?
Python 2.7 program
How about printing to
2 decimal places?

10. Formatted Output
Python 2.7 program

11. Formatted Output: floating point (f)
$100 principal for 10 years at 4% (0.04) compound interest = $148.02

12. Formatted Output Lots of ways: (Old way)
notation comes originally from the C Programming Language:
sprintf function

13. Now use instead: <template-string>.format(<values>)
Formatted Output
Now use instead: <template-string>.format(<values>)
%<width>.<precision><type>
<type> = d, f, s
<width> = minimum number of characters; right-justified by default, -width => left-justified 0 = as wide as needed
<precision> = number of places after decimal point
e.g. 02d two digits wide, pad with 0 if needed

14. Formatted Output: examples
Function str() coerces integer or float above into type 'str'

15. Formatted Output Newer way:
formatting
Use {} for each argument
(can be numbered, e.g. {0}, {1},… or referenced by keyword {x})
{:width}

16. Formatted Output {0:..} and {1:…} index into the format arguments
0 in {0:..} can be omitted but not the colon

17. A note on string encoding
Python 2.7
Python 3.x