A string = 1 2 3 4
Program should return = [[1,2],[3,4]]
in python
I want the string to be converted into a list of every two element from string
You could go for something very simple such as:
s = "10 2 3 4 5 6 7 8"
l = []
i = 0
list_split_str = s.split() # splitting the string according to spaces
while i < len(s) - 1:
l.append([s[i], s[i + 1]])
i += 2
This should output:
[['10', '2'], ['3', '4'], ['5', '6'], ['7', '8']]
You could also do something a little more complex like this in a two-liner:
list_split = s.split() # stripping spaces from the string
l = [[a, b] for a, b in zip(list_split[0::2], list_split[1::2])]
The slice here means that the first list starts at index zero and has a step of two and so is equal to [10, 3, 5, ...]. The second means it starts at index 1 and has a step of two and so is equal to [2, 4, 6, ...]. So we iterate over the first list for the values of a and the second for those of b.
zip returns a list of tuples of the elements of each list. In this case, [('10', '2'), ('3', '4'), ('5', '6'), ...]. It allows us to group the elements of the lists two by two and iterate over them as such.
This also works on lists with odd lengths.
For example, with s = "10 2 3 4 5 6 7 ", the above code would output:
[['10', '2'], ['3', '4'], ['5', '6']]
disregarding the 7 since it doesn't have a buddy.
here is the solution if the numbers exact length is divisible by 2
def every_two_number(number_string):
num = number_string.split(' ')
templist = []
if len(num) % 2 == 0:
for i in range(0,len(num),2):
templist.append([int(num[i]),int(num[i+1])])
return templist
print(every_two_number('1 2 3 4'))
you can remove the if condition and enclosed the code in try and except if you want your string to still be convert even if the number of your list is not divisible by 2
def every_two_number(number_string):
num = number_string.split(' ')
templist = []
try:
for i in range(0,len(num),2):
templist.append([int(num[i]),int(num[i+1])])
except:
pass
return templist
print(every_two_number('1 2 3 4 5'))
Related
So I am practicing in hacker earth and I have to take two inputs in a single line separated by space.
The below code is what I used:
x, y = [x for x in input("Enter two value: ").split()]
It is supposed to take input that looks like '2 5'
And it is returning an error:
Execution failed
ValueError : not enough values to unpack (expected 2, got 1)
Stack Trace:
Traceback (most recent call last):
File "/tmp/165461120/user_code.py", line 13, in
x, y = [x for x in input("Enter two value: ").split()]
ValueError: not enough values to unpack (expected 2, got 1)
What I think I understood is that it is giving two values as a single string. If so how do I take separate them and convert them into integers?
To take two inputs
x, y = input("Enter two value: ").split()
This should do the trick. To convert to int you can do it seprately on the both x and y.
Or better way is to use a map function
x, y = map(int, input().split())
For your case, only typecasting is remaining, so that splitted numbers becomes int. So, just you have to add
x, y = [int(x) for x in input("Enter two value: ").split()]
Alternatively, For taking 2 inputs in single line, you can use map also
x, y = map(int, input().split())
This is happening because Hacker Earth, in almost all cases, gives its input line by line.
In almost all cases, the inputs are of the form below.
1
2 3 4
5
6 7 8
This will differ on problem by problem basis and needs to be personalized for each problem.
You are getting the error not enough values to unpack because Hacker Earth is giving only a single input, and you are expecting 2. If it had been more than 2, then the error would have been too many values to unpack.
In all probability its because you are trying to input the number of test cases, which is the first input, and a single number input, in most hacker earth problems.
Process-01 : using list comprehension
whole_line = input() # 1 2 3 4 5
strings = whole_line.split(' ') # ['1', '2', '3', '4', '5']
# remove extra space within numbers if any from list
numbers = [int(num) for num in strings if len(num)>0] # [1, 2, 3, 4, 5]
print(numbers) # [1, 2, 3, 4, 5]
Now you can write down the whole logic within one line like below
numbers = [ int(num) for num in input().split(' ') if len(num)>0 ]
print(numbers)
Process-02 : using filter and map function
whole_line = input() # 1 2 3 4 5
strings = whole_line.split(' ') # ['1', '2', '3', '4', '5']
# remove extra space within numbers if any from list
strings = list(filter(lambda x :len(x)>0 ,strings))
numbers = list(map(int,strings)) # convert each string to int
print(numbers) # [1, 2, 3, 4, 5]
Now you can write down the whole logic within one line like below
numbers = list(map(int,filter(lambda x : len(x)>0,input().split(' '))))
print(numbers)
In [20]: a,b = raw_input().split()
12 12.2
In [21]: a = int(a)
Out[21]: 12
In [22]: b = float(b)
Out[22]: 12.2
You can't do this in a one-liner (or at least not without some super duper extra hackz0r skills -- or semicolons), but python is not made for one-liners.
In order to put the input into a list:
numbersList = [int(n) for n in input('Enter numbers: ').split()]
Can someone explain what does 'int(n) for n in' mean?
How do I improve this question?
The entire expression is referred to as a List Comprehension. It's a simpler, Pythonic approach to construct a for loop that iterates through a list.
https://www.pythonforbeginners.com/basics/list-comprehensions-in-python
Given your code:
numbersList = [int(n) for n in input('Enter numbers: ').split()]
Lets say you run the code provided, you get a prompt for input:
Enter numbers: 10 8 25 33
Now what happens is, Python's input() function returns a string, as documented here:
https://docs.python.org/3/library/functions.html#input
So the code has now essentially become this:
numbersList = [int(n) for n in "10 8 25 33".split()]
Now the split() function returns an array of elements from a string delimited by a given character, as strings.
https://www.pythonforbeginners.com/dictionary/python-split
So now your code becomes:
numbersList = [int(n) for n in ["10", "8", "25", "33"]]
This code is now the equivalent of:
numbersAsStringsList = ["10", "8", "25", "33"]
numberList = []
for n in numbersAsStringsList:
numberList.append(int(n))
The int(n) method converts the argument n from a string to an int and returns the int.
https://docs.python.org/3/library/functions.html#int
For example input('Enter numbers: ').split() returns an array of strings like ['1', '4', '5']
int(n) for n in will loop throug the array and turn each n into an integer while n will be the respective item of the array.
let us try to understand this list comprehension expression though a simple piece of code which means the same thing.
nums = input('Enter numbers: ') # suppose 5 1 3 6
nums = nums.split() # it turns it to ['5', '1', '3', '6']
numbersList = [] # this is list in which the expression is written
for n in nums: # this will iterate in the nums.
number = int(n) # number will be converted from '5' to 5
numbersList.append(number) # add it to the list
print(numbersList) # [5, 1, 3, 6]
I have a list,
A = ['A','B','C','D','E','F','G','H']
if user input x = 4, then I need an output that shows every value that is 4 distance away from each other.
If starting from 'A' after printing values that are 4 distance away from each other ie: {'A', 'E'}, the code should iterate back and start from 'B' to print all values from there ie: {'B', 'F'}
No number can be in more than one group
Any help is going to be appreciated since I am very new to python.
this is what I have done
x = input("enter the number to divide with: ")
A = ['A','B','C','D','E','F','G','H']
print("Team A is divided by " +x+ " groups")
print("---------------------")
out = [A[i] for i in range(0, len(A), int(x))]
print(out)
My code is printing only the following when user input x =4
{'A', 'E'}
But I need it to look like the following
{'A', 'E'}
{'B', 'F'}
{'C', 'G'}
{'D', 'H'}
what am I doing wrong?
Use zip:
out = list(zip(A, A[x:]))
For example:
x = 4 # int(input("enter the number to divide with: "))
A = ['A','B','C','D','E','F','G','H']
print(f"Team A is divided by {x} groups")
print("---------------------")
out = list(zip(A, A[x:]))
print(out)
Outputs:
[('A', 'E'), ('B', 'F'), ('C', 'G'), ('D', 'H')]
Here you have the live example
If you want to keep the comprehension:
out = [(A[i], A[i+x]) for i in range(0, len(A)-x)]
**You can find my answer below.
def goutham(alist):
for passchar in range(0,len(alist)-4):
i = alist[passchar]
j = alist[passchar+4]
print("{"+i+","+j+"}")
j = 0
alist = ['a','b','c','d','e','f','g','h']
goutham(alist)
I am using Python 3.6 and I have a list of dictionaries like this:
list = [{'name': 'A', 'number':'1'}, {'name': 'B', 'number':'2'}, {'name': 'C', 'number':'3'}, {'name': 'D', 'number':'4'}]
I found out how to print the list in the desired format with:
for s in list:
name = s['name']
number = s['number']
print(name + " = "+ number)
Which gives:
A = 1
B = 2
C = 3
D = 4
I would like to be able to multiply the items 'number' by 2 for example and display:
A = 2
B = 4
C = 6
D = 8
Thank you!
Are you trying to temporarily multiply the values and print them out? Which in this case, you would change your last line to
print(name + " = "+ int(number) * 2)
However, if you want to multiply the values in your dictionary directly, you would go about it as so:
for s in list:
name = s['name']
s['number'] = str(int(s['number']) * 2) # multiply value by 2
number = s['number']
print(name + " = "+ number)
Note that your problem may arise from the fact that your dictionary values are stored as strings instead of integers, which means that to perform any kind of mathematical operation on them, you must convert them to an integer and back to a string.
You're able to multiply a number by using the * symbol 2 * 2 will output 4.
Because your values are stored as Strings you'll need to convert them to Integers first. int('2') * 2 == 4.
Then to print an Integer with a string you need to convert it back to a string.
for the last line change it to
print(name + " = "+ str(int(number)*2))
You can always iterate over your list to modify the value of its nested parts, i.e.:
your_list = [{'name': 'A', 'number': '1'},
{'name': 'B', 'number': '2'},
{'name': 'C', 'number': '3'},
{'name': 'D', 'number': '4'}]
for item in your_list: # iterate over each dictionary in your_list
# since your dict contains strings we have to convert the value into a number/integer
# before multiplying it by 2
item["number"] = int(item["number"]) * 2 # turn it back to a string with str() if needed
# now, let's demonstrate that the data changed in `your_list`:
for item in your_list: # iterate over each dictionary in your_list
print("{} = {}".format(item["name"], item["number"])) # print in your desired format
# A = 2
# B = 4
# C = 6
# D = 8
Based on my little knowledge on pandas，pandas.Series.str.contains can search a specific str in pd.Series. But what if the dataframe is large and I just want to glance all kinds of str element in it before I do anything?
Example like this:
pd.DataFrame({'x1':[1,2,3,'+'],'x2':[2,'a','c','this is']})
x1 x2
0 1 2
1 2 a
2 3 c
3 + this is
I need a function to return ['+','a','c','this is']
If you are looking strictly at what are string values and performance is not a concern, then this is a very simple answer.
df.where(df.applymap(type).eq(str)).stack().tolist()
['a', 'c', '+', 'this is']
There are 2 possible ways - check numeric values saved as strings or not.
Check difference:
df = pd.DataFrame({'x1':[1,'2.78','3','+'],'x2':[2.8,'a','c','this is'], 'x3':[1,4,5,4]})
print (df)
x1 x2 x3
0 1 2.8 1
1 2.78 a 4 <-2.78 is float saved as string
2 3 c 5 <-3 is int saved as string
3 + this is 4
#flatten all values
ar = df.values.ravel()
#errors='coerce' parameter in pd.to_numeric return NaNs for non numeric
L = np.unique(ar[np.isnan(pd.to_numeric(ar, errors='coerce'))]).tolist()
print (L)
['+', 'a', 'c', 'this is']
Another solution is use custom function for check if possible convert to floats:
def is_not_float_try(str):
try:
float(str)
return False
except ValueError:
return True
s = df.stack()
L = s[s.apply(is_not_float_try)].unique().tolist()
print (L)
['a', 'c', '+', 'this is']
If need all values saved as strings use isinstance:
s = df.stack()
L = s[s.apply(lambda x: isinstance(x, str))].unique().tolist()
print (L)
['2.78', 'a', '3', 'c', '+', 'this is']
You can using str.isdigit with unstack
df[df.apply(lambda x : x.str.isdigit()).eq(0)].unstack().dropna().tolist()
Out[242]: ['+', 'a', 'c', 'this is']
Using regular expressions and set union, could try something like
>>> set.union(*[set(df[c][~df[c].str.findall('[^\d]+').isnull()].unique()) for c in df.columns])
{'+', 'a', 'c', 'this is'}
If you use a regular expression for a number in general, you could omit floating point numbers as well.