Develop Reference

How do I get the position of a string inside a list in Python? [duplicate]

This question already has answers here:
How to get the position of a character in Python?
(11 answers)
Closed 1 year ago.
I am trying to get the position of a string inside a list in Python? How should I do it?
For example, when a user provides a sentence "Hello my name is Dolfinwu", I turn the entire sentence into a list beforehand, and I want to get the positions of each "o" right here, how can I do it? In this case, the position of the first "o" is "4", and the position of the second "o" is "18". But obviously, users would enter different sentences by using different words, so how can I get a specific string value's position under this unpredictable situation?
I have tried this code as below. I know it contains syntax errors, but I could not figure out something better.
sentence = input('Please type a sentence: ')
space = ' '
for space in sentence:
if space in sentence:
space_position = sentence[space]
print(space_position)

How about this one? I figured another solution out yesterday.
import re
sentence = input('Please type a sentence: ')
print([match.span()[0] for match in re.finditer(' ', sentence)])

This code of yours is messed up a bit
space = ' ' # This is fine but redundant
for space in sentence: # Shouldn't reuse variable names. Should be <for char in sentence. But I wouldn't use that either since we don't need the char it self but the index
if space in sentence: #Should be <if char == space> Your just returns a True if there's a single space anywhere in the string. Assuming it's using the correct variable named space. Honestly I don't know what this code will do since I didn't run it :P
space_position = sentence[space]
print(space_position)
Here's what I would do, which could be done better since I'm a beginner too.
sentence = input('Please type a sentence: ')
for i in range(len(sentence)):
if sentence[i] == " ":
print(i)
#>>>Please type a sentence: A sentence and spaces
#>>>1
#>>>10
#>>>14

There is also an error in your first code, where the line space_position = sentence[space] uses a string, if I am correct, as the index of the list in the line, which I believe should be an integer. So what I would do would be like
sentence = input('Please type a sentence: ') # Asks the user to input the sentence
space_position = [] # The list where the list indexes of the spaces will be stored (can work for any other symbol)
for i in range(len(sentence)): # Scans every single index of the list
if sentence[i] == " ": # Determines whether if the value of the specific list index is the chosen string value
# (The value could be swapped for another one aside from strings)
print(i) # Print out the index where the value is the chosen string value
The rest of the cost are like what #pudup posted
P.S. I am also a beginner, so my code may not be the best solution or have syntax errors, apologies if they do not work or are not very efficient.

Capitalizing the beginning of sentences in Python

The following code is for an assignment that asks that a string of sentences is entered from a user and that the beginning of each sentence is capitalized by a function.
For example, if a user enters: 'hello. these are sample sentences. there are three of them.'
The output should be: 'Hello. These are sample sentences. There are three of them.'
I have created the following code:
def main():
sentences = input('Enter sentences with lowercase letters: ')
capitalize(sentences)
#This function capitalizes the first letter of each sentence
def capitalize(user_sentences):
sent_list = user_sentences.split('. ')
new_sentences = []
count = 0
for count in range(len(sent_list)):
new_sentences = sent_list[count]
new_sentences = (new_sentences +'. ')
print(new_sentences.capitalize())
main()
This code has two issues that I am not sure how to correct. First, it prints each sentence as a new line. Second, it adds an extra period at the end. The output from this code using the sample input from above would be:
Hello.
These are sample sentences.
There are three of them..
Is there a way to format the output to be one line and remove the final period?

The following works for reasonably clean input:
>>> s = 'hello. these are sample sentences. there are three of them.'
>>> '. '.join(x.capitalize() for x in s.split('. '))
'Hello. These are sample sentences. There are three of them.'
If there is more varied whitespace around the full-stop, you might have to use some more sophisticated logic:
>>> '. '.join(x.strip().capitalize() for x in s.split('.'))
Which normalizes the whitespace which may or may not be what you want.

def main():
sentences = input('Enter sentences with lowercase letters: ')
capitalizeFunc(sentences)
def capitalizeFunc(user_sentences):
sent_list = user_sentences.split('. ')
print(".".join((i.capitalize() for i in sent_list)))
main()
Output:
Enter sentences with lowercase letters: "hello. these are sample sentences. there are three of them."
Hello.These are sample sentences.There are three of them.

I think this might be helpful:
>>> sentence = input()
>>> '. '.join(map(lambda s: s.strip().capitalize(), sentence.split('.')))

>>> s = 'hello. these are sample sentences. there are three of them.'
>>> '. '.join(map(str.capitalize, s.split('. ')))
'Hello. These are sample sentences. There are three of them.'

This code has two issues that I am not sure how to correct. First, it prints each sentence as a new line.
That’s because you’re printing each sentence with a separate call to print. By default, print adds a newline. If you don’t want it to, you can override what it adds with the end keyword parameter. If you don’t want it to add anything at all, just use end=''
Second, it adds an extra period at the end.
That’s because you’re explicitly adding a period to every sentence, including the last one.
One way to fix this is to keep track of the index as well as the sentence as you’re looping over them—e.g., with for index, sentence in enumerate(sentences):. Then you only add the period if index isn’t the last one. Or, slightly more simply, you add the period at the start, if the index is anything but zero.
However, theres a better way out of both of these problems. You split the string into sentences by splitting on '. '. You can join those sentences back into one big string by doing the exact opposite:
sentences = '. '.join(sentences)
Then you don’t need a loop (there’s one hidden inside join of course), you don’t need to worry about treating the last or first one special, and you only have one print instead of a bunch of them so you don’t need to worry about end.
A different trick is to put the cleverness of print to work for you instead of fighting it. Not only does it add a newline at the end by default, it also lets you print multiple things and adds a space between them by default. For example, print(1, 2, 3) or, equivalently, print(*[1, 2, 3]) will print out 1 2 3. And you can override that space separator with anything else you want. So you can print(*sentences, sep='. ', end='') to get exactly what you want in one go. However, this may be a bit opaque or over-clever to people reading your code. Personally, whenever I can use join instead (which is usually), I do that even though it’s a bit more typing, because it makes it more obvious what’s happening.
As a side note, a bit of your code is misleading:
new_sentences = []
count = 0
for count in range(len(sent_list)):
new_sentences = sent_list[count]
new_sentences = (new_sentences +'. ')
print(new_sentences.capitalize())
The logic of that loop is fine, but it would be a lot easier to understand if you called the one-new-sentence variable new_sentence instead of new_sentences, and didn’t set it to an empty list at the start. As it is, the reader is led to expect that you’re going to build up a list of new sentences and then do something with it, but actually you just throw that list away at the start and handle each sentence one by one.
And, while we’re at it, you don’t need count here; just loop over sent_list directly:
for sentence in sent_list:
new_sentence = sent + '. '
print(new_sentence.capitalize())
This does the same thing as the code you had, but I think it’s easier to understand that it does that think from a quick glance.
(Of course you still need the fixes for your two problems.)

Use nltk.sent_tokenize to tokenize the string into sentences. And capitalize each sentence, and join them again.
A sentence can't always end with a ., there can other things too, like a ?, or !. Also three consecutive dots ..., doesn't end the sentence. sent_tokenize will handle them all.
from nltk.tokenize import sent_tokenize
def capitalize(user_sentences):
sents = sent_tokenize(user_sentences)
capitalized_sents = [sent.capitalize() for sent in sents]
joined_ = ' '.join(capitalized_sents)
print(joined_)
The reason your sentences were being printed on separate lines, were because print always ends its output with a newline. So, printing sentences separately in loop will make them print on newlines. So, you should print them all at once, after joining them. Or, you can specify end='' in print statement, so it doesn't end the sentences with newline characters.
The second thing, about output being ended with an extra period, is because, you're appending '. ' with each of the sentence. The good thing about sent_tokenize is, it doesn't remove '.', '?', etc from the end of the sentences, so you don't have to append '. ' at the end manually again. Instead, you can just join the sentences with a space character, and you'll be good to go.
If you get an error for nltk not being recognized, you can install it by running pip install nltk on the terminal/cmd.

How to print random items from a dictionary?

everyone. I'm trying to complete a basic assignment. The program should allow a user to type in a phrase. If the phrase contains the word "happy" or "sad", that word should then be randomly replaced by a synonym (stored in a dictionary). The new phrase should then be printed out. What am I doing wrong? Every time I try to run it, the program crashes. This is the error I get:
0_part1.py", line 13, in <module>
phrase["happy"] = random.choice(thesaurus["happy"])
TypeError: 'str' object does not support item assignment
Here is what I have so far:
import random
thesaurus = {
"happy": ["glad", "blissful", "ecstatic", "at ease"],
"sad": ["bleak", "blue", "depressed"]
}
phrase = input("Enter a phrase: ")
phrase2 = phrase.split(' ')
if "happy" in phrase:
phrase["happy"] = random.choice(thesaurus["happy"])
if "sad" in phrase:
phrase["sad"] = random.choice(thesaurus["sad"])
print(phrase)

The reason for your error is that phrase is a string, and strings are immutable. On top of that, strings are sequences, not mappings; you can index them or slice them (e.g., happy_index = phrase.find("happy"); phrase[happy_index:happy_index+len("happy")]), but you can't use them like dictionaries.
If you want to create a new string, replacing the substring happy with another word, use the replace method.
And there's no reason to check first; if happy isn't found, replace wil do nothing.
So:
phrase = phrase.replace("happy", random.choice(thesaurus["happy"]))
While we're at it, instead of explicitly looking up each key, you may want to loop over the dictionary and apply all the synonyms:
for key, replacements in thesaurus.items():
phrase = phrase.replace(key, random.choice(replacements))
Finally, notice that this code will replace all instances of happy with the same replacement. Which I think your intended code was also trying to do. If you want to replace each of them with a separately randomly-chosen synonym, that's a bit more complicated. You could loop over phrase.find("happy", offset) until it returns -1, but a neat trick might make it simpler: split the string around each instance of happy, substitute in a different synonym for each split part, then join them all back together. Like this:
parts = phrase.split("happy")
parts[:-1] = [part + random.choice(thesaurus["happy"]) for part in parts[:-1]]
phrase = ''.join(parts)

Generate a random number from (0..[size of list - 1]). Then, access that index of the list. To get the length of a list, just do len(list_name).

using find in python

New to python, my assignment asks to ask user for input and then find and print the first letter of each word in the sentence
so far all I have is
phrase = raw_input("Please enter a sentence of 3 or 4 words: ")
^ That is all I have. So say the user enters the phrase "hey how are you" I am supposed to find and print the first letter of every word so it would print "hhay"
I know how to index if it is a string that the programmer types but not when a user inputs the data.

This does everything that Ming said in a single line.
You can very well understand this code if you read his explanation.
phrase = raw_input("Please enter a sentence of 3 or 4 words: ")
output = ''.join([x[0] for x in phrase.split()])
print output
Update related to comment (Considers only first 3 words):
output = ''.join([x[0] for x in phrase.split()])[:3]
Ignoring the last word (Total number of words doesn't matter)
output = ''.join([x[0] for x in phrase.split()])[:-1]

Here are a rough outline of the steps you can take. Since this is an assignment, I will leave actually assembling them into a working program up to you.
raw_input will produce a string.
If you have two strings, one in foo and one in bar, then you can call string.split as foo.split(bar), and the result of that will be a list of strings resulting from splitting the contents of foo by the separator bar. For example, 'a b c'.split(' ') == ['a', 'b', 'c'].
You can slice a string with brackets to retrieve particular characters from it, counting from zero in the leftmost position. For example, 'abcd'[0] == 'a'.
If you have a string foo and a list of strings bar, then you can call string.join as foo.join(bar) to produce a single string of the elements of foo glued together with bar. For example, 'x'.join(['a', 'b', 'c']) == 'axbxc'.
You can print the constructed output.
This is of course only one of many approaches you could take.

As an answer to your question "For the next one I have to join the first letters of only the first 3 words and ignore the 4th word. How do I do that?"
output = ''.join([x[0] for x in phrase.split()[0:3]])
If instead it is first character of all word but the last then use :
output = ''.join([x[0] for x in phrase.split()[0:len(phrase.split()) - 1]])

How might I create an acronym by splitting a string at the spaces, taking the character indexed at 0, joining it together, and capitalizing it?

My code
beginning = input("What would you like to acronymize? : ")
second = beginning.upper()
third = second.split()
fourth = "".join(third[0])
print(fourth)
I can't seem to figure out what I'm missing. The code is supposed to the the phrase the user inputs, put it all in caps, split it into words, join the first character of each word together, and print it. I feel like there should be a loop somewhere, but I'm not entirely sure if that's right or where to put it.

Say input is "Federal Bureau of Agencies"
Typing third[0] gives you the first element of the split, which is "Federal". You want the first element of each element in the sprit. Use a generator comprehension or list comprehension to apply [0] to each item in the list:
val = input("What would you like to acronymize? ")
print("".join(word[0] for word in val.upper().split()))
In Python, it would not be idiomatic to use an explicit loop here. Generator comprehensions are shorter and easier to read, and do not require the use of an explicit accumulator variable.

When you run the code third[0], Python will index the variable third and give you the first part of it.
The results of .split() are a list of strings. Thus, third[0] is a single string, the first word (all capitalized).
You need some sort of loop to get the first letter of each word, or else you could do something with regular expressions. I'd suggest the loop.
Try this:
fourth = "".join(word[0] for word in third)
There is a little for loop inside the call to .join(). Python calls this a "generator expression". The variable word will be set to each word from third, in turn, and then word[0] gets you the char you want.

works for me this way:
>>> a = "What would you like to acronymize?"
>>> a.split()
['What', 'would', 'you', 'like', 'to', 'acronymize?']
>>> ''.join([i[0] for i in a.split()]).upper()
'WWYLTA'
>>>

One intuitive approach would be:
get the sentence using input (or raw_input in python 2)
split the sentence into a list of words
get the first letter of each word
join the letters with a space string
Here is the code:
sentence = raw_input('What would you like to acronymize?: ')
words = sentence.split() #split the sentece into words
just_first_letters = [] #a list containing just the first letter of each word
#traverse the list of words, adding the first letter of
#each word into just_first_letters
for word in words:
just_first_letters.append(word[0])
result = " ".join(just_first_letters) #join the list of first letters
print result

#acronym2.py
#illustrating how to design an acronymn
import string
def main():
sent=raw_input("Enter the sentence: ")#take input sentence with spaces
for i in string.split(string.capwords(sent)):#split the string so each word
#becomes
#a string
print string.join(i[0]), #loop through the split
#string(s) and
#concatenate the first letter
#of each of the
#split string to get your
#acronym
main()

name = input("Enter uppercase with lowercase name")
print(f'the original string = ' + name)
def uppercase(name):
res = [char for char in name if char.isupper()]
print("The uppercase characters in string are : " + "".join(res))
uppercase(name)