I want to write a function that takes a list of words and keys and outputs those keys as dictionary keys with any words starting with that letter attached.
How could this be achieved using simple python 3 code?
eg. takes (['apples', 'apple', 'bananna', 'fan'], 'fad')
returns {'a' : ['apple', 'apples'], 'f' : ['fan']}
so far i have tried:
def dictionary(words, char_keys)
char_keys = remove_duplicates(char_keys)
ret = {}
keys_in_dict = []
words = sorted(words)
for word in words:
if word[0] in char_keys and word[0] not in keys_in_dict:
ret[word[0]] = word
keys_in_dict.append(word[0])
elif word[0] in keys_in_dict:
ret[word[0]] += (word)
return ret
This gives kinda the right output but it the output is in a single string rather than a list of strings.(the def is not indented properly i know)
If the input is a list of strings, you can check if the char is in the dict, if yes, append the word, otherwise add a list with the word:
def dictionary(inpt):
result = {}
for word in inpt:
char = word[0]
if char in result:
result[char].append(word)
else:
result[char] = [word]
return result
The modern way to do this is to use a collections.defaultdict with list as argument.
def dictionary(inpt):
result = defaultdict(list)
for word in inpt:
result[word[0]].append(word)
return result
Not sure if your list of inputs are consisted with only strings or it can also include sub-lists of strings (and I'm not so sure why "fad" disappeared in your example). Obviously, in the latter scenario it will need some more effort. For simplicity I assume if contains only strings and here's a piece of code which hopefully points the direction:
d = {}
for elem in input_list[0]:
if elem[0] in input_list[1]
lst = d.get(elem[0], [])
lst.append(elem)
d[elem] = lst
Related
Can someone explain to me why there is a difference in output when using nested loops vs nested list comprehension?
letters = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
def unique_english_letters (word) :
unique = []
for i in word:
if i not in unique:
unique.append(i)
return len(unique)
print(unique_english_letters("mississippi"))
# outputs 4 (my expected output)
letters = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
def unique_english_letters (word) :
unique = []
unique = [i for i in word if i not in unique]
return len(unique)
print(unique_english_letters("mississippi"))
#outputs 11 (length of mississippi"
^ Output
In the second example, this:
unique = []
unique = [i for i in word if i not in unique]
is equivalent to:
unique = [i for i in word if i not in []]
unique is an empty list while the list comprehension is evaluated, and then unique is re-assigned the results.
To do what you want in simple terms, use a set which can only contain unique values, and use set intersection(& operator) to generate the set of letters contained in word:
letters = set("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz")
def unique_english_letters(word):
return len(letters & set(word))
print(unique_english_letters("mississippi"))
# output: 4
(Im using python on Jupiter Notebook 5.7.8)
I have a project in which are 3 lists, and a list(list_of_lists) that refer to those 3.
I want my program to receive an input, compare this input to the content of my "list_of_lists" and if find a match I want to store the match in another variable for later use.
Im just learning, so here is the code I wrote:
first = ["item1", "item2","item3"]
second = ["item4","item5","item6"]
list1 = [first,second]
list2 = ["asd","asd","asd"]
list_of_lists = [list1,list2]
x = input("Which list are you going to use?: ")
for item in list_of_lists:
if item == x:
match = item
print(match)
print('There was a match')
else:
print('didnt match')
I expect a match but it always output "the didnt match",
I assume it fail to compare the contect of the input with the list inside the list_of lists. The question is also why and how to do it properly(if possible), thanks.
input in python3 returns a string. if you want to convert it into a list, use ast.literal_eval or json.loads or your own parsing method.
list_str = input("Which list are you going to use?: ")
user_list = ast.literal_eval(list_str)
assert isinstance(user_list, list)
...
# do your thing...
So here i tried this code, and it does what i desire, I dont know if its too rudimentary and if there is another way to achieve this.
Here I use a second list to catch the moment when there is a match, after I give to that list the value of my true list and from there print it to be used.
I was wondering if there is a way to take out of the ressults the symbols "[]" and the quotes '', so I can have a clean text format, thanks for the help
first = ["item1", "item2","item3"]
second = ["item4","item5","item6"]
list1 = [first,second]
list2 = ["asd","asd","asd"]
list3 = ["qwe","qwe","qwe"]
list_of_lists = [list1,list2,list3]
reference_list = ["list1","list2","list3"]
count = -1
x = input('Which list are you going to use? ')
for item in reference_list:
count += 1
if x == item:
reference_list = list_of_lists
print(reference_list[count])
I am learning about list comprehension therefore i would like to recreate the code without list comprehension.
The code is the following:
items=[x for x in input().split(",")]
items.sort()
print (items)
This is how i recreated it:
print ("Enter comma seperated words: ")
userinput = input ().split(",")
words = []
for i in range (len(userinput)):
words.append(userinput)
words.sort()
print (words)
I expect the output should be in alphabetical order but it does not.
Let's say our input is this...
userinput = 'foo,bar'
Using the list comprehension code...
items=[x for x in userinput.split(",")]
items.sort()
print (items)
Output becomes: `['bar', 'foo']`
However, if we use your recreated code..
userinput = userinput.split(',')
words = []
for i in range (len(userinput)):
words.append(userinput)
words.sort()
print (words)
Output becomes: `[['foo', 'bar']]
Why is this?
When the line userinput = userinput.split(',') is run, userinput now becomes ['foo', 'bar'].
Therefore, when words.append(userinput) is run, what it is actually doing is saying words.append(['foo', 'bar']), and thus you are appending a list into a list meaning that words = [['foo', 'bar']].
words.sort() will not sort nested lists within itself, therefore, your list isnt sorted.
Therefore the fix is to append each element of userinput into words instead of appending userinput as a list into words.
userinput = userinput.split(',')
words = []
for i in range (len(userinput)):
words.append(userinput[i])
words.sort()
print (words)
Output becomes: ['bar', 'foo']
I'm doing some python challenges for fun and I've found a challenge which tells me to make a program that takes an input and prints the numbers in the message.
but when I run the program it prints nothing but [] in the same number as the letters in the message, and also it do not recognize if a letter is actually a number or not, it just see every letter as a string and prints empty squares.
Here's the code:
WORDS = []
NUMBERS = []
Sentence = input()
for item in Sentence:
if item == str():
WORDS.append(item)
if item == int():
NUMBERS.append(item)
print(('[%s]' % ', '.join(map(str, NUMBERS))))
Have any ideas?
Here is probably what you meant. You have to split the sentence first.
All of the resulting items will be of type string, therefore isinstance will not help.
str.isdigit() checks if a string contains only digits. If it is a number, you can convert it to an integer using int.
WORDS = []
NUMBERS = []
Sentence = input()
for item in Sentence.split():
if item.isdigit():
NUMBERS.append(int(item))
else:
WORDS.append(item)
print(('[%s]' % ', '.join(map(str, NUMBERS))))
If you do not do the split first, it will work too, but give you just single characters in the WORDS list and single numbers in the NUMBERS list.
Typechecking is usually done using isinstance(obj, cls) :
x = 42
print(isinstance(x, int))
print(isinstance(x, str))
but in your case this will not work since input() always returns a string (a string composed of numeric characters is still a string), so the proper solution is to check if the string is composed only of numeric characters (and eventually build an int from it if you need proper ints).
Also, input() returns a single string, and from your namings (WORDS) I assume you want to iterate on the distinct words, not on each characters like you actually do:
words = []
numbers = []
sentence = input()
for item in sentence.strip().split():
if item.isnumeric():
numbers.append(int(item))
else:
words.append(item)
print(('[%s]' % ', '.join(map(str, numbers))))
Use the built-in isinstance function:
if isinstance(item, str):
WORDS.append(item)
if isinstance(item, int):
NUMBERS.append(item)
I'm in the process of learning python and with a practical example I've come across a problem I cant seem to find the solution for.
The error I get with the following code is
'list' object has to attribute 'upper'.
def to_upper(oldList):
newList = []
newList.append(oldList.upper())
words = ['stone', 'cloud', 'dream', 'sky']
words2 = (to_upper(words))
print (words2)
Since the upper() method is defined for string only and not for list, you should iterate over the list and uppercase each string in the list like this:
def to_upper(oldList):
newList = []
for element in oldList:
newList.append(element.upper())
return newList
This will solve the issue with your code, however there are shorter/more compact version if you want to capitalize an array of string.
map function map(f, iterable). In this case your code will look like this:
words = ['stone', 'cloud', 'dream', 'sky']
words2 = list(map(str.upper, words))
print (words2)
List comprehension [func(i) for i in iterable].In this case your code will look like this:
words = ['stone', 'cloud', 'dream', 'sky']
words2 = [w.upper() for w in words]
print (words2)
You can use the list comprehension notation and apply theupper method to each string in words:
words = ['stone', 'cloud', 'dream', 'sky']
words2 = [w.upper() for w in words]
Or alternatively use map to apply the function:
words2 = list(map(str.upper, words))
AFAIK, upper() method is implemented for strings only. You have to call it from each child of the list, and not from the list itself.
It's great that you're learning Python! In your example, you are trying to uppercase a list. If you think about it, that simply can't work. You have to uppercase the elements of that list. Additionally, you are only going to get an output from your function if you return a result at the end of the function. See the code below.
Happy learning!
def to_upper(oldList):
newList = []
for l in oldList:
newList.append(l.upper())
return newList
words = ['stone', 'cloud', 'dream', 'sky']
words2 = (to_upper(words))
print (words2)
Try it here!