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How to count words that end with a letter? (python)

I am a beginner and this is what I came up with so far. However, it does not output the correct number of words that end with "a" or "b." Any tips on how to correct this code?
names = input("Enter list of names: ")
name = names.split(" ")
num = len(name)
ab = ""
print("Number of words:", num)
for i in range(num):
if name[i] == ' ':
if name[i-1] == a:
ab.append() + " "
elif name[i-1] == b:
ab.append() + " "
a_b = ab.split(' ')
print("Number of words that end with a or b: ",len(a_b))

In Python boolean (True and False) are the same as the integers 1 and 0. This means you can use sum() to count True booleans. str.endswith() returns a boolean. This means you can just do this:
words = ["stab", "drama", "hello", "magma", "test"]
a_b = sum(word.endswith(('a', 'b')) for word in words)
# 3
z_c = sum(word.endswith(('z', 'c')) for word in words)
# 0

Any tips on how to correct this code?
Others have answered alternative, working solutions, but I want to try to point out the specific things wrong in your code snippet and tips to correct.
First here's a copy of your snippet with some simple debugging prints along with their output (running in python 3.10).
names = "Barry Lima Bab"
name = names.split(" ")
print(f"{name=}") # name=['Barry', 'Lima', 'Bab']
num = len(name)
print(f"{num=}") # num=3
ab = ""
print("Number of words:", num)
for i in range(num):
print(name[i]) # Barry -> Lima -> Bab
if name[i] == ' ':
if name[i-1] == a:
ab.append() + " "
elif name[i-1] == b:
ab.append() + " "
print(f"{ab=}") # ab=''
a_b = ab.split(' ')
print(f"{a_b=}") # a_b=['']
Breaking things down step by step like this is a great starting point for better understanding what's going on.
if name[i] == ' ': Notice the value of name[i] so this check never resolves to True meaning the code inside never runs
if the inner code did run, you'd hit a NameError: name 'a' is not defined. Did you mean: 'ab'? because a is undefined. Probably meant 'a' here. same for b
In my example, name[i-1] would be 'Bab' -> 'Barry' -> 'Lima' which is probably not what you're expecting. This is because you're getting the -1th, 0th, 1st items in name. to get the last letter from the name, you want name[i][-1] here
if you then get into either of the furthest inside conditions, you'd encounter AttributeError: 'str' object has no attribute 'append' which happens because append is for list not str. You couldchange ab to be a list to use this in which case you'd want ab.append(name[i]) or you can use string concatenation like ab += " " + name[i] or using str.concat
1 last note of interest, you may have noticed your code as-is really likes to return and say that there's 1 item. This is because the above issues always (if the program doesn't break) leaves ab == '' and ''.split(' ') => [''] and thus len(ab.split(" ")) => 1
1 tip that I think would help in code comprehension is that the name variable here is not a single name string like it implies. It's actually a list[str]. I'd probably denote the variables something more like names_str: str vs names: list[str] or raw_names vs names. Then just use something like for name in names: and not worry about indexes. You can also use name.endswith('a') instead of name[-1] == 'a' for better readability.
Eventually you can combine these into a list comprehension for maximal succinctness -> len([name for name in names if name.endswith('a') or name.endswith('b')]).

words = ["ab", "bab", "pa", "pap"]
result = 0
for word in words:
if word[-1] in "ab":
result += 1
print(result)

As a list comprehension:
words = ["word1a", "word2b", "word3", "word4", "word5a"] # ['word1a', 'word2b', 'word5a']
filtered_words = [word for word in words if word[-1] in "ab"]
filtered_words = [word for word in words if word.endswith(("a", "b"))] # better, if you have multiple endings you want to search for with different lengths
len(filtered_words) # 3

name[i-1] is the previous name in the list, not the last character of the current name in the loop.
There's no need to append the matching names to a string. If you just need the count of matches, increment a counter variable.
You need to put a and b in quotes to make them strings, not variables.
names = input("Enter list of names: ")
name = names.split(" ")
matches = 0
print("Number of words:", len(name))
for cur_name in name:
if cur_name.endswith('a') or cur_name.endswith('b'):
matches += 1
print("Number of words that end with a or b: ", matches)

Use the endswith string method to detect if the last letter is "a" or "b"
names = ["bob","boba","larry","curly","moe"]
count = 0
for name in names:
if name.endswith("a") or name.endswith("b"):
count += 1
print(f"{count=}") # count=2

Appending a char to an empty list

I am very new to programming, so sorry for a basic question. I am trying to write a function that will take a string in which words are divided by ',' and return a list of these words (the Split method). My code is:
def str_to_list(my_shop_str):
my_shop_list = ['']
word_in_list = 0
for letter in my_shop_str:
if letter != ',':
my_shop_list[word_in_list] += letter
else:
word_in_list += 1
my_shop_list + ['']
return my_shop_list
print(str_to_list("Milk,Cottage,Tomatoes")) should look like [Milk, Cottage, Tomatoes]
but I am keep getting IndexError: list index out of range.
I read some answers here and couldn't find something to work.
Can anyone explain what is wrong.

list has the method append so a solution will be something like this:
def str_to_list(my_shop_str):
my_shop_list = ['']
word_in_list = 0
for letter in my_shop_str:
if letter != ',':
my_shop_list[word_in_list] += letter
else:
word_in_list += 1
my_shop_list.append('')
return my_shop_list
PS: Do not forgot about empty spaces between words in string like "aaa, bbb, ccc" will be ['aaa', ' bbb', ' ccc'] with spaces.

def sp(s):
l =[]
while True:
comma = s.find(',')
if comma == -1:
l.append(s)
break
l.append(s[:comma])
s = s[comma+1:]
print(l)
this is a simplified version hope it helps.

Simplest Way:
We can use an inbuilt split function.
def Convert(string):
# split the string whenever "," occurs
# store the splitted parts in a list
li = list(string.split(","))
return li
# Driver code
str1 = "Hello,World"
print(Convert(str1))
Output:
["Hello", "World"]

Split a string, loop through it character by character, and replace specific ones?

I'm working on an assignment and have gotten stuck on a particular task. I need to write two functions that do similar things. The first needs to correct capitalization at the beginning of a sentence, and count when this is done. I've tried the below code:
def fix_capitalization(usrStr):
count = 0
fixStr = usrStr.split('.')
for sentence in fixStr:
if sentence[0].islower():
sentence[0].upper()
count += 1
print('Number of letters capitalized: %d' % count)
print('Edited text: %s' % fixStr)
Bu receive an out of range error. I'm getting an "Index out of range error" and am not sure why. Should't sentence[0] simply reference the first character in that particular string in the list?
I also need to replace certain characters with others, as shown below:
def replace_punctuation(usrStr):
s = list(usrStr)
exclamationCount = 0
semicolonCount = 0
for sentence in s:
for i in sentence:
if i == '!':
sentence[i] = '.'
exclamationCount += 1
if i == ';':
sentence[i] = ','
semicolonCount += 1
newStr = ''.join(s)
print(newStr)
print(semicolonCount)
print(exclamationCount)
But I'm struggling to figure out how to actually do the replacing once the character is found. Where am I going wrong here?
Thank you in advance for any help!

I would use str.capitalize over str.upper on one character. It also works correctly on empty strings. The other major improvement would be to use enumerate to also track the index as you iterate over the list:
def fix_capitalization(s):
sentences = [sentence.strip() for sentence in s.split('.')]
count = 0
for index, sentence in enumerate(sentences):
capitalized = sentence.capitalize()
if capitalized != sentence:
count += 1
sentences[index] = capitalized
result = '. '.join(sentences)
return result, count
You can take a similar approach to replacing punctuation:
replacements = {'!': '.', ';': ','}
def replace_punctuation(s):
l = list(s)
counts = dict.fromkeys(replacements, 0)
for index, item in enumerate(l):
if item in replacements:
l[index] = replacements[item]
counts[item] += 1
print("Replacement counts:")
for k, v in counts.items():
print("{} {:>5}".format(k, v))
return ''.join(l)

There are better ways to do these things but I'll try to change your code minimally so you will learn something.
The first function's issue is that when you split the sentence like "Hello." there will be two sentences in your fixStr list that the last one is an empty string; so the first index of an empty string is out of range. fix it by doing this.
def fix_capitalization(usrStr):
count = 0
fixStr = usrStr.split('.')
for sentence in fixStr:
# changed line
if sentence != "":
sentence[0].upper()
count += 1
print('Number of letters capitalized: %d' % count)
print('Edited text: %s' % fixStr)
In second snippet you are trying to write, when you pass a string to list() you get a list of characters of that string. So all you need to do is to iterate over the elements of the list and replace them and after that get string from the list.
def replace_punctuation(usrStr):
newStr = ""
s = list(usrStr)
exclamationCount = 0
semicolonCount = 0
for c in s:
if c == '!':
c = '.'
exclamationCount += 1
if c == ';':
c = ','
semicolonCount += 1
newStr = newStr + c
print(newStr)
print(semicolonCount)
print(exclamationCount)
Hope I helped!

Python has a nice build in function for this
for str in list:
new_str = str.replace('!', '.').replace(';', ',')
You can write a oneliner to get a new list
new_list = [str.replace('!', '.').replace(';', ',') for str in list]
You also could go for the split/join method
new_str = '.'.join(str.split('!'))
new_str = ','.join(str.split(';'))
To count capitalized letters you could do
result = len([cap for cap in str if str(cap).isupper()])
And to capitalize them words just use the
str.capitalize()
Hope this works out for you

How to remove NUL characters from a string in Python? [duplicate]

This simple code that simply tries to replace semicolons (at i-specified postions) by colons does not work:
for i in range(0,len(line)):
if (line[i]==";" and i in rightindexarray):
line[i]=":"
It gives the error
line[i]=":"
TypeError: 'str' object does not support item assignment
How can I work around this to replace the semicolons by colons? Using replace does not work as that function takes no index- there might be some semicolons I do not want to replace.
Example
In the string I might have any number of semicolons, eg "Hei der! ; Hello there ;!;"
I know which ones I want to replace (I have their index in the string). Using replace does not work as I'm not able to use an index with it.

Strings in python are immutable, so you cannot treat them as a list and assign to indices.
Use .replace() instead:
line = line.replace(';', ':')
If you need to replace only certain semicolons, you'll need to be more specific. You could use slicing to isolate the section of the string to replace in:
line = line[:10].replace(';', ':') + line[10:]
That'll replace all semi-colons in the first 10 characters of the string.

You can do the below, to replace any char with a respective char at a given index, if you wish not to use .replace()
word = 'python'
index = 4
char = 'i'
word = word[:index] + char + word[index + 1:]
print word
o/p: pythin

Turn the string into a list; then you can change the characters individually. Then you can put it back together with .join:
s = 'a;b;c;d'
slist = list(s)
for i, c in enumerate(slist):
if slist[i] == ';' and 0 <= i <= 3: # only replaces semicolons in the first part of the text
slist[i] = ':'
s = ''.join(slist)
print s # prints a:b:c;d

If you want to replace a single semicolon:
for i in range(0,len(line)):
if (line[i]==";"):
line = line[:i] + ":" + line[i+1:]
Havent tested it though.

You cannot simply assign value to a character in the string.
Use this method to replace value of a particular character:
name = "India"
result=name .replace("d",'*')
Output: In*ia
Also, if you want to replace say * for all the occurrences of the first character except the first character,
eg. string = babble output = ba**le
Code:
name = "babble"
front= name [0:1]
fromSecondCharacter = name [1:]
back=fromSecondCharacter.replace(front,'*')
return front+back

This should cover a slightly more general case, but you should be able to customize it for your purpose
def selectiveReplace(myStr):
answer = []
for index,char in enumerate(myStr):
if char == ';':
if index%2 == 1: # replace ';' in even indices with ":"
answer.append(":")
else:
answer.append("!") # replace ';' in odd indices with "!"
else:
answer.append(char)
return ''.join(answer)

to use the .replace() method effectively on string without creating a separate list
for example take a look at the list username containing string with some white space, we want to replace the white space with an underscore in each of the username string.
names = ["Joey Tribbiani", "Monica Geller", "Chandler Bing", "Phoebe Buffay"]
usernames = []
to replace the white spaces in each username consider using the range function in python.
for name in names:
usernames.append(name.lower().replace(' ', '_'))
print(usernames)
Or if you want to use one list:
for user in range(len(names)):
names[user] = names[user].lower().replace(' ', '_')
print(names)

How about this:
sentence = 'After 1500 years of that thinking surpressed'
sentence = sentence.lower()
def removeLetter(text,char):
result = ''
for c in text:
if c != char:
result += c
return text.replace(char,'*')
text = removeLetter(sentence,'a')

If you are replacing by an index value specified in variable 'n', then try the below:
def missing_char(str, n):
str=str.replace(str[n],":")
return str

To replace a character at a specific index, the function is as follows:
def replace_char(s , n , c):
n-=1
s = s[0:n] + s[n:n+1].replace(s[n] , c) + s[n+1:]
return s
where s is a string, n is index and c is a character.

I wrote this method to replace characters or replace strings at a specific instance. instances start at 0 (this can easily be changed to 1 if you change the optional inst argument to 1, and test_instance variable to 1.
def replace_instance(some_word, str_to_replace, new_str='', inst=0):
return_word = ''
char_index, test_instance = 0, 0
while char_index < len(some_word):
test_str = some_word[char_index: char_index + len(str_to_replace)]
if test_str == str_to_replace:
if test_instance == inst:
return_word = some_word[:char_index] + new_str + some_word[char_index + len(str_to_replace):]
break
else:
test_instance += 1
char_index += 1
return return_word

You can do this:
string = "this; is a; sample; ; python code;!;" #your desire string
result = ""
for i in range(len(string)):
s = string[i]
if (s == ";" and i in [4, 18, 20]): #insert your desire list
s = ":"
result = result + s
print(result)

names = ["Joey Tribbiani", "Monica Geller", "Chandler Bing", "Phoebe Buffay"]
usernames = []
for i in names:
if " " in i:
i = i.replace(" ", "_")
print(i)
Output:
Joey_Tribbiani
Monica_Geller
Chandler_Bing
Phoebe_Buffay

My problem was that I had a list of numbers, and I only want to replace a part of that number, soy I do this:
original_list = ['08113', '09106', '19066', '17056', '17063', '17053']
# With this part I achieve my goal
cves_mod = []
for i in range(0,len(res_list)):
cves_mod.append(res_list[i].replace(res_list[i][2:], '999'))
cves_mod
# Result
cves_mod
['08999', '09999', '19999', '17999', '17999', '17999']

Even more simpler:
input = "a:b:c:d"
output =''
for c in input:
if c==':':
output +='/'
else:
output+=c
print(output)
output: a/b/c/d

i tried using this instead as a 2 in 1
usernames = ["Joey Tribbiani", "Monica Geller", "Chandler Bing", "Phoebe Buffay"]
# write your for loop here
for user in range(0,len(usernames)):
usernames[user] = usernames[user].lower().replace(' ', '_')
print(usernames)

Cleaner way to replace character at a specific index
def replace_char(str , index , c):
return str[:index]+c+str[index+1:]

Find out word at specific index

I have a string with multiple words separated by underscores like this:
string = 'this_is_my_string'
And let's for example take string[n] which will return a letter.
Now for this index I want to get the whole word between the underscores.
So for string[12] I'd want to get back the word 'string' and for string[1] I'd get back 'this'

Very simple approach using string slicing is to:
slice the list in two parts based on position
split() each part based on _.
concatenate last item from part 1 and first item from part 2
Sample code:
>>> my_string = 'this_is_my_sample_string'
# ^ index 14
>>> pos = 14
>>> my_string[:pos].split('_')[-1] + my_string[pos:].split('_')[0]
'sample'

This shuld work:
string = 'this_is_my_string'
words = string.split('_')
idx = 0
indexes = {}
for word in words:
for i in range(len(word)):
idx += 1
indexes[idx] = word
print(indexes[1]) # this
print(indexes[12]) #string

The following code works. You can change the index and string variables and adapt to new strings. You can also define a new function with the code to generalize it.
string = 'this_is_my_string'
sp = string.split('_')
index = 12
total_len = 0
for word in sp:
total_len += (len(word) + 1) #The '+1' accounts for the underscore
if index < total_len:
result = word
break
print result

A little bit of regular expression magic does the job:
import re
def wordAtIndex(text, pos):
p = re.compile(r'(_|$)')
beg = 0
for m in p.finditer(text):
#(end, sym) = (m.start(), m.group())
#print (end, sym)
end = m.start()
if pos < end: # 'pos' is within current split piece
break
beg = end+1 # advance to next split piece
if pos == beg-1: # handle case where 'pos' is index of split character
return ""
else:
return text[beg:end]
text = 'this_is_my_string'
for i in range(0, len(text)+1):
print ("Text["+str(i)+"]: ", wordAtIndex(text, i))
It splits the input string at '_' characters or at end-of-string, and then iteratively compares the given position index with the actual split position.