ITEC 109 2014spring ibarland

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lab02-function-call
Calling a function
abs, ord, pickAFile

• What two types of values do we have, in python?
• What two things does + mean, depending on context? Give an example of each.
• Discuss error messages, from last time.
• One more type: character (kinda like a string of length exactly-one). We use single-quotes to indicate a character (or “char”).

  Examples:

  • 'A'
  • 'a'
  • '7' — This is a piece of text; it's like a key on the keyboard. It is not a number! If you want to talk about the number, you must leave off the quotes. (In general, quote-marks mean you're talking about the exact characters/words used, and not what they mean. That's true both in English, and in programming.)
  • '+' — Again, this is a piece of text — it's data — not a math operator. If you want to talk about the math operator, leave off the quotes.
  • ' ' (space)
  • '\n' (newline). The book has more about backslash being use as a “character escape code”; there are other less common ones.

  Updated list: In Python, we have several types of values:

  • integers (“ints”): e.g. 17, 9999, -5, 0, 23423423432234234
  • characters: e.g. 'A', '+', ' ', '\n'.
  • strings: e.g. "aloha", "Individual characters, strung together!"

calling functions

• pow(2,10)
• len("hello"), len("!"), and even len("").
  • What type do of information we give to len?
  • What type of answer does len give back to us?
• ord('A').

  Even if we don't really know what ord's answer means, we can still know:

  • What type do of information we give to ord?
  • What type of answer does ord give back to us?

• chr(65)

• import string # This loads the entire library of string functions. Only needed once per session. string.capitalize("hello") # The name of the function is kind of long, because it includes the library-name at the start: “string.capitalize”

• TODO What is the ascii value (as given by ord) for the letter Z? Write a python function-call to tell you.
• TODO There are many, many more python functions. Google “python math functions”, and follow the first link. Find the description of pow.
• TODO What is the square-root of 2?

  hint: Looking at the web-page from the previous step, can you find a different¹ function, which computes the square-root? Can you call that function, giving it the number 2, as its input?

The last example — the square root of two — illustrates one more type of data that python has: “floating point numbers”, which is a number with a decimal-point². They commonly called “float”s or “double”s³.

Updated list: In Python, we have several types of values:

• integers (“ints”): e.g. 17, 9999, -5, 0, 23423423432234234
• floating-point numbers (“double”s): e.g. 2.4, -23.4, 4.0, 6.023e23.
• characters: e.g. 'A', '+', ' ', '\n'.
• strings: e.g. "aloha", "Individual characters, strung together!"

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©2013, Ian Barland, Radford University Last modified 2014.Jan.27 (Mon)

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