Count the uppercase letters in a string with Python

Question

You can do this with sum, a generator expression, and str.isupper:

message = input("Type word: ")

print("Capital Letters: ", sum(1 for c in message if c.isupper()))

See a demonstration below:

>>> message = input("Type word: ")
Type word: aBcDeFg
>>> print("Capital Letters: ", sum(1 for c in message if c.isupper()))
Capital Letters:  3
>>>

You can use re:

import re
string = "Not mAnY Capital Letters"
len(re.findall(r'[A-Z]',string))

5

Using len and filter :

import string
value = "HeLLo Capital Letters"
len(filter(lambda x: x in string.uppercase, value))
>>> 5

I've done some comparisons of the methods above + RE compiled using Python 3.7.4
For this, I've used the book Alice’s Adventures in Wonderland, by Lewis Carroll from Project Gutenberg.

from urllib.request import urlopen

# Download 
text = urlopen('https://www.gutenberg.org/files/11/11-0.txt').read().decode('utf-8')
# Split it into the separate chapters and remove table of contents, etc
sep = 'CHAPTER'
chaps = [sep + ch for ch in text.split('CHAPTER') if len(ch) > 1000]
len(chaps)

Defined all approaches as functions in order to use them in the loop and keep succinct.

import re
import string

def py_isupper(text): 
    return sum(1 for c in text if c.isupper())

def py_str_uppercase(text):
    return sum(1 for c in text if c in string.ascii_uppercase)

def py_filter_lambda(text):
    return len(list(filter(lambda x: x in string.ascii_uppercase, text)))

def regex(text):
    return len(re.findall(r'[A-Z]',text))

# remove compile from the loop
REGEX = re.compile(r'[A-Z]')
def regex_compiled(text):
    return len(REGEX.findall(text))

The results are below.

%%timeit
cnt = [py_isupper(ch) for ch in chaps]

7.84 ms ± 69.7 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)

%%timeit
cnt = [py_str_uppercase(ch) for ch in chaps]

11.9 ms ± 94.6 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)

%%timeit
cnt = [py_filter_lambda(ch) for ch in chaps]

19.1 ms ± 499 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)

%%timeit
cnt = [regex(ch) for ch in chaps]

1.49 ms ± 13 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)

%%timeit
cnt = [regex_compiled(ch) for ch in chaps]

1.45 ms ± 8.69 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)

from string import ascii_uppercase
count = len([letter for letter in instring if letter in ascii_uppercase])

This is not the fastest way, but I like how readable it is. Another way, without importing from string and with similar syntax, would be:

count = len([letter for letter in instring if letter.isupper()])

def n_lower_chars(string):
    return sum(i.isupper() for i in string)

sums up the numbers of True values in the generator expression