The question I'm asking is why do we use temporary variables after taking an input? For example: In the code down below, we've requested a 'num' from the customer. Then we've changed into it a 'temp'. Why don't we simply continue with 'num'? I can't see any aim into changing it a different variable. Why don't the code work if we don't make this swap? Thanks.
It is beacause in the while cycle in the last row you change the value of temp so if instead of temp you use num you will change its value and in the if else statement you can't compare the sum with the input number.
Related
I am using Python. I would like to create a new column which is the log transformation of column 'lights1992'.
I am using the following code:
log_lights1992 = np.log(lights1992)
I obtain the following error:
I have tried two things: 1) adding a 1 to each value and transform the column 'lights1992' to numeric.
city_join['lights1992'] = pd.to_numeric(city_join['lights1992'])
city_join["lights1992"] = city_join["lights1992"] + 1
However, that two solution has not worked. Variable 'lights1992' is a float64 type. Do you know what can be the problem?
Edit:
The variable 'lights1992' comes from doing a zonal_statistics from a raster 'junk1992', maybe this affect.
zs1 = zonal_stats(city_join, junk1992, stats=['mean'], nodata=np.nan)
city_join['lights1992'] = [x['mean'] for x in zs1]
the traceback states:
'DatasetReader' object has no attribute'log'.
Did you re-assign numpy to something else at some point? I can't find much about 'DatasetReader' is that a custom class?
EDIT:
I think you would need to pass the whole column because your edit doesn't show a variable named 'lights1992'
so instead of:
np.log(lights1992)
can you try passing in the Dataframe's column to log?:
np.log(city_join['lights1992'])
2ND EDIT:
Since you've reported back that it works I'll dive into the why a little bit.
In your original statement you called the log function and gave it an argument, then you assigned the result to a variable name:
log_lights1992 = np.log(lights1992)
The problem here is that when you give python text without any quotes it thinks you are giving it a variable name (see how you have log_lights1992 on the left of the equal sign? You wanted to assign the results of the operation on the right hand side of the equal sign to the variable name log_lights1992) but in this case I don't think lights1992 had any value!
So there were two ways to make it work, either what I said earlier:
Instead of giving it a variable name you give .log the column of the city_join dataframe (that's what city_join["lights1992"]) directly.
Or
You assign the value of that column to the variable name first then you pass it in to .log, like this:
lights1992 = city_join["lights1992"]
log_lights1992 = np.log(lights1992)
Hope that clears it up for you!
Given an array of integers, return indices of the two numbers such that they add up to a specific target.
,in each input would have not use the same element twice.
class solution():
def __init__(self,array_num,target_num):
self.array_num=array_num
self.target_num=target_num
for t in self.array_num:
for b in self.array_num:
e=t+b
w=self.array_num.index(t),self.array_num.index(b)
y=list(w)
if e==self.target_num:
if y==[0,0]:
break
else:
print(y)
p=[3,3]
so=solution(p,6)
output
[] or nothing
expected output
[0,1]
The problem is that you are asking the list to give you the index if a number like this:
self.array_num.index(t)
This will always give you the first occurrence, which is 0 here, although the loop is actually at the second position with index 1.
To avoid that, reverse the logic: create the loop for the index (use len() and range()), then get the number at that position.
As this question sounds like homework or school assignment, I'll not post a full solution. It should be possible to solve the problem now.
More hints to make your teacher happy:
[0, 0] is not the only solution that results in 6. You want to exclude other invalid combinations as well. Pro tip: there's a nice solution that doesn't require any check and will run faster. It's easy to find once you switched the logic.
Currently you do all work in the constructor of the object. Maybe you want a method that does the actual calculation.
Your variable names are not self-explaining. Don't use so many single letter variables.
I want to do a function that takes in a 2D table, which represents a magic square, and check if all numbers between 1 and size*size are in the table.
Any ideas for an effective way to write my function?
Assuming your 'tab' variable is a list, something like this should work:
for x in range(1, size*size+1):
if x not in tab:
print(f"{x} not in list")
break
If you want it to tell you every missing number, remove the break. The break makes it more efficient if you just want to check whether it is a valid list or not, so it will only tell you the first missing number.
I wonder if you can help because I've been looking at this for a good half hour and I'm completely baffled, I think I must be missing something so I hope you can shed some light on this.
In this area of my program I am coding a query which will search a list of tuples for the salary of the person. Each tuple in the list is a separate record of a persons details, hence I have used two indexes; one for the record which is looped over, and one for the salary of the employee. What I am aiming for is for the program to ask you a minimum and maximum salary and for the program to print the names of the employees who are in that salary range.
It all seemed to work fine, until I realised that when entering in the value '100000' as a maximum value the query would output nothing. Completely baffled I tried entering in '999999' which then worked and all records were print. The only thing that I can think of is that the program is ignoring the extra digit, which I could not figure out why this would be?!
Below is my code for that specific section and output for a maximum value of 999999 (I would prefer not to paste the whole program as this is for a coursework project and I want to prevent anyone on the same course potentially copying my work, sorry if this makes my question unclear!):
The maximum salary out of all the records is 55000, hence why it doesnt make sense that a minimum of 0 and maximum of 100000 does not work, but a maximum of 999999 does!
If any more information is need to help, please ask! This probably seems unclear but like I said above, I dont want anyone from the class to plagiarise and my work to be void because of that! So I have tried to ask this without posting all my code on here!
Given your use of the print function (instead of the Python 2 print statement), it looks like you're writing Python 3 code. In Python 3, input returns a str. I'm guessing your data is also storing the salaries as str (otherwise the comparison would raise a TypeError). You need to convert both stored values and the result of input to int so it performs numerical comparisons, not ASCIIbetical comparisons.
When you read in from standard input in Python, no matter what input you get, you receive the input as a string. That means that your comparison function is resulting to:
if tuplist[x][2] > "0" and tuplist[x][2] < "999999" :
Can you see what the problem is now? Because it's a homework assignment, I don't want to give you the answer straight away.
I have a variable in a NetCDF file that has a default value if the variable is null. How do you remove this value or change it to 0 when the variable is missing a value?
It sounds like the problem is that when the variable is populated into the NetCDF file, it is set to insert some default value for values that are missing. Now, I am assuming that you need to remove these default values after the file has been written and you are working with the data.
So (depending on how you are accessing the variable) I would pull the variable out of the NetCDF file and assign it to a python variable. This is the first method that comes to mind.
Use a for loop to step through and replace that default value with 0
variable=NetCDF_variable #Assume default value is 1e10
cleaned_list=[]
for i in variable:
if i == 1e10:
cleaned_list.append(0) #0 or whatever you want to fill here
else:
cleaned_list.append(i)
If the default value is a float, you may want to look into numpy.isclose if the above code isn't working. You might also be interested in masking your data in case any computations you do would be thrown off by inserting a 0.
EDIT: User N1B4 provided a much cleaner and efficient way of doing the exact same thing as above.
variable[variable == 1e10] = 0