python how to uppercase some characters in string

Question

Here is what I want to do but doesn\'t work:

mystring = \"hello world\"
toUpper = [\'a\', \'e\', \'i\', \'o\', \'u\', \'y\']
array = list(mystring)

for c in arr         


        

Answer 1

You can use the str.translate() method to have Python replace characters by other characters in one step.

Use the string.maketrans() function to map lowercase characters to their uppercase targets:

try:
    # Python 2
    from string import maketrans
except ImportError:
    # Python 3 made maketrans a static method
    maketrans = str.maketrans 

vowels = 'aeiouy'
upper_map = maketrans(vowels, vowels.upper())
mystring.translate(upper_map)

This is the faster and more 'correct' way to replace certain characters in a string; you can always turn the result of mystring.translate() into a list but I strongly suspect you wanted to end up with a string in the first place.

Demo:

>>> try:
...     # Python 2
...     from string import maketrans
... except ImportError:
...     # Python 3 made maketrans a static method
...     maketrans = str.maketrans 
... 
>>> vowels = 'aeiouy'
>>> upper_map = maketrans(vowels, vowels.upper())
>>> mystring = "hello world"
>>> mystring.translate(upper_map)
'hEllO wOrld'