Question

This assignment is based on Exercise 8.4 from your textbook. Each of the following Python functions is supposed to check whether its argument has any lowercase letters.
For each function, describe what it actually does when called with a string argument. If it does not correctly check for lowercase letters, give an example argument that produces incorrect results, and describe why the result is incorrect.

# 1

def any_lowercase1(s):
for c in s:
if c.islower():
return True
else:
return False


# 2

def any_lowercase2(s):
for c in s:
if 'c'.islower():
return 'True'
else:
return 'False'


# 3

def any_lowercase3(s):
for c in s:
flag = c.islower()
return flag


# 4

def any_lowercase4(s):
flag = False
for c in s:
flag = flag or c.islower()
return flag


# 5

def any_lowercase5(s):
for c in s:
if not c.islower():
return False
return True

Answer 1

Explanation:

#1 is wrong because if the first character is not lowercase, it stops and returns false, ignoring all the other characters. It can be fixed by removing the else: statement and moving the return False statement outside of the loop.

This is efficient; if one lowercase character is encountered, the function 'knows enough' and can return true. Only if no lowercase is encountered it has to loop all the way to the end.

You can try this out on repl.it.

Many of the others functions have problems in them. #4 looks OK.