How to apply a for loop to a string in Python

Question

How do I apply a for loop to a string in Python which allows me to count each letter in a word? The ultimate goal is to discover the most common letter.

This is the code so far:

 print "Type 'exit' at any time to exit the program."

 continue_running = True
 while continue_running:


word = raw_input("Please enter a word: ")
if word == "exit":
    continue_running = False

else:
    while not word.isalpha():
        word = raw_input("ERROR: Please type a single word containing alphabetic characters only:")
    print word

    if len(word) == 1:
        print word + " has " + str(len(word)) + " letter."
    else:
        print word + " has " + str(len(word)) + " letters."

    if sum(1 for v in word.upper() if v in ["A", "E", "I", "O", "U"]) == 1:
        print "It also has ", sum(1 for v in word.upper() if v in ["A", "E", "I", "O", "U"]), " vowel."
    else:
        print "It also has ", sum(1 for v in word.upper() if v in ["A", "E", "I", "O", "U"]), " vowels."

    if sum(1 for c in word if c.isupper()) == 1:
        print "It has ", sum(1 for c in word if c.isupper()), " capital letter."
    else:
        print "It has ", sum(1 for c in word if c.isupper()), " capital letters."

    for loop in word:

I know I can use the:

(collections.Counter(word.upper()).most_common(1)[0])

format, but this isn't the way I want to do it.

Example added, last line of code is the only problem.

poddpython
– poddpython

2015-03-10 12:03:03 +00:00
Commented Mar 10, 2015 at 12:03 — poddpython
– poddpython, Commented Mar 10, 2015 at 12:03

Martijn Pieters · Accepted Answer · 2015-03-10 12:24:29Z

3

You can simply loop directly over strings; they are sequences just like lists and tuples; each character in the string is a separate element:

for character in word.upper():
    # count the character.

Counts can then be collected in a dictionary:

counts = {}
for character in word.upper():
    # count the character.
    counts[character] = counts.get(character, 0) + 1

after which you'd pick the most common one; you can use the max() function for that:

most_common = max(counts, key=counts.__getitem__)  # maximum by value

Demo:

>>> word = 'fooBARbazaar'
>>> counts = {}
>>> for character in word.upper():
...     # count the character.
...     counts[character] = counts.get(character, 0) + 1
... 
>>> counts
{'A': 4, 'B': 2, 'F': 1, 'O': 2, 'R': 2, 'Z': 1}
>>> max(counts, key=counts.__getitem__)
'A'

edited Mar 10, 2015 at 12:24

answered Mar 10, 2015 at 11:56

Martijn Pieters

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21 Comments

poddpython Over a year ago

How could I use this to help me count characters from word?

poddpython Over a year ago

Sorry, I'm fairly new to this. I have written the first two pieces of code you wrote and ran the module, and nothing has happened.

Martijn Pieters Over a year ago

@poddpython: did you try to print anything? Something probably happened, but if you don't produce output to show anything you won't notice.

poddpython Over a year ago

word.upper() is the correct thing, I'm just struggling to get this to work. Sorry

poddpython Over a year ago

I just got something, I'll edit the question for you to see. :)

|

Heisenberg · Accepted Answer · 2015-03-10 12:21:03Z

0

If you don't want to re-invent the wheel try using Counter

>>> from collections import Counter
>>> x = Counter("stackoverflow")
>>> x
Counter({'o': 2, 'a': 1, 'c': 1, 'e': 1, 'f': 1, 'k': 1, 'l': 1, 's': 1, 'r': 1, 't': 1, 'w': 1, 'v': 1})
>>> print max(x, key=x.__getitem__)
o
>>>

answered Mar 10, 2015 at 12:21

Heisenberg

1,5083 gold badges19 silver badges36 bronze badges

1 Comment

Martijn Pieters Over a year ago

The OP managed to remove that again from their question, but they explicitly stated they did not want to use a Counter(). Also, why are you ignoring the Counter.most_common() method to get the most common character?

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