Basic Python Question on String operations: example: string.lowercase

Question

So I'm trying to run this, but it errors out and I need help understanding what's wrong. I really appreciate any help, I'm taking the MIT opencourseware intro to programming:

words="GreatTimes"
words.lowercase

And I get this error:

AttributeError: 'str' object has no attribute 'lowercase'

The issue is that I'm trying to run example code from "How to think like a computer scientist" and it still gives me the error.

def isLower(ch):
    return string.find(string.lowercase, ch) != -1

So I can't figure out what the syntax error is. Looking at the Python doc page it says this:

string.lowercase A string containing all the characters that are considered lowercase letters. On most systems this is the string 'abcdefghijklmnopqrstuvwxyz'. The specific value is locale-dependent, and will be updated when locale.setlocale() is called.

Thoughts?

Edit: Ah, sorry I should be more clear. So I'm trying to write a piece of code that will tell me whether or not a character in a string is lowercase or not. my code is my implementation of it. while the example code is something i'm using to try to check to see if my syntax is wrong and that is the source of the problem. However, the example code also generates an error. In a nutshell, why doesn't this code work? It seems like it Should spit out a string of all the lowercase letters like "reatimes" from "GreatTimes" And/or how would you use string.lowercase to make this program?

Answer 1

I'm a bit confused by what you are trying to do. This seems like a rather contrived exercise.

• If you just want to use an instance method, words.lower() will return a lowercase version of the string words.

• If you want to implement a lowercase function of your own using string.lowercase (which is just a constant set to a string of all lowercase letters), then you need to make sure you do an import string before calling it (e.g. in your lower function example).

• If you did an import string, you could also use string.lower('STRING with CAPS') instead.

Edit: Here's some code that runs your function, to show you it works:

import string

def isLower(ch):
    return string.find(string.lowercase, ch) != -1


words = "GreatTimes"

lowercase_letters = ""
for ch in words:
    print ch, '->', isLower(ch)

    if isLower(ch):
        lowercase_letters += ch

print "Lowercase letters were:", lowercase_letters

Output:

G -> False
r -> True
e -> True
a -> True
t -> True
T -> False
i -> True
m -> True
e -> True
s -> True
Lowercase letters were: reatimes

Answer 2

lowercase is the name of a string in the string module:

import string string.lowercase 'abcdefghijklmnopqrstuvwxyz'

but you can't access it through a string instance:

word = 'this is a string' word.lowercase Traceback (most recent call last): File "", line 1, in AttributeError: 'str' object has no attribute 'lowercase'

Also, the find method doesn't do what you think -- check the docs.

Allen

Answer 3

Try to use "ascii.lowercase" it works