Split One Column to Multiple Columns in Pandas - python

I want to split one current column into 3 columns. In screenshot we see the builder column, which need to be split in 3 more column such as b.name , city and country. So I use str.split() method in python to split the column which give me good result for 2 column ownerName = df['owner_name'] df[["ownername", "owner_country"]] = df["owner_name"].str.split("-", expand=True)
But when it come to three columns ownerName = df['owner_name'] df[["ownername", "city", "owner_country"]] = df["owner_name"].str.split("," ,"-", expand=True), where I use 2 delimiter ',' and '-' it give me this error:
File "C:\Users....\lib\site-packages\pandas\core\frame.py", line 3160, in setitem
self._setitem_array(key, value)
File "C:\Users....\lib\site-packages\pandas\core\frame.py", line 3189, in _setitem_array
raise ValueError("Columns must be same length as key")
ValueError: Columns must be same length as key
whats best solution for 2 delimiter ',' and '-', Also there is some empty rows too.

Your exact input is unclear, but assuming the sample input kindly provided by #ArchAngelPwn, you could use str.split with a regex:
names = ['Builder_Name', 'City_Name', 'Country']
out = (df['Column1']
.str.split(r'\s*[,-]\s*', expand=True) # split on "," or "-" with optional spaces
.rename(columns=dict(enumerate(names))) # rename 0/1/2 with names in order
)
output:
Builder_Name City_Name Country
0 Builder Name City Country

You can combine some rows if you feel like you need to, but this was a possible options and should be pretty readable for most developers included in the projects
data = {
'Column1' : ['Builder Name - City, Country']
}
df = pd.DataFrame(data)
df['Builder_Name'] = df['Column1'].apply(lambda x : x.split('-')[0])
df['City_Name'] = df['Column1'].apply(lambda x : x.split('-')[1:])
df['City_Name'] = df['City_Name'][0]
df['City_Name'] = df['City_Name'].apply(lambda x : x.split()[0])
df['City_Name'] = df['City_Name'].apply(lambda x : x.replace(',', ''))
df['Country'] = df['Column1'].apply(lambda x : x.split(',')[1])
df = df[['Builder_Name', 'City_Name', 'Country']]
df

As mentioned in questions there is 2 delimiter "-" and ",". for one we simply use str.split("-", expand=True) and for 2 different delimiter we can use same code with addition of small code such as column1 = name-city name ,country (Owner = SANTIERUL NAVAL CONSTANTA - CONSTANTZA, ROMANIA) code will be write as ownerName = df['owner_name'] df[["Owner_name", "City_Name", "owner_country"]] = df["owner_name"].str.split(r', |- |\*|\n', expand=True)

Related

How to add prefix to the selected records in python pandas df

I have df where some of the records in the column contains prefix and some of them not. I would like to update records without prefix. Unfortunately, my script adds desired prefix to each record in df:
new_list = []
prefix = 'x'
for ids in df['ids']:
if ids.find(prefix) < 1:
new_list.append(prefix + ids)
How can I ommit records with the prefix?
I've tried with df[df['ids'].str.contains(prefix)], but I'm getting an error.
Use Series.str.startswith for mask and add values with numpy.where:
df = pd.DataFrame({'ids':['aaa','ssx','xwe']})
prefix = 'x'
df['ids'] = np.where(df['ids'].str.startswith(prefix), '', prefix) + df['ids']
print (df)
ids
0 xaaa
1 xssx
2 xwe

Rename columns in dataframe using bespoke function python pandas

I've got a data frame with column names like 'AH_AP' and 'AH_AS'.
Essentially all i want to do is swap the part before the underscore and the part after the underscore so that the column headers are 'AP_AH' and 'AS_AH'.
I can do that if the elements are in a list, but i've no idea how to get that to apply to column names.
My solution if it were a list goes like this:
columns = ['AH_AP','AS_AS']
def rejig_col_names():
elements_of_header = columns.split('_')
new_title = elements_of_header[-1] + "_" + elements_of_header[0]
return new_title
i'm guessing i need to apply this to something like the below, but i've no idea how, or how to reference a single column within df.columns:
df.columns = df.columns.map()
Any help appreciated. Thanks :)
You can do it this way:
Input:
df = pd.DataFrame(data=[['1','2'], ['3','4']], columns=['AH_PH', 'AH_AS'])
print(df)
AH_PH AH_AS
0 1 2
1 3 4
Output:
df.columns = df.columns.str.split('_').str[::-1].str.join('_')
print(df)
PH_AH AS_AH
0 1 2
1 3 4
Explained:
Use string accessor and the split method on '_'
Then using the str accessor with index slicing reversing, [::-1], you
can reverse the order of the list
Lastly, using the string accessor and join, we can concatenate the
list back together again.
You were almost there: you can do
df.columns = df.columns.map(rejig_col_names)
except that the function gets called with a column name as argument, so change it like this:
def rejig_col_names(col_name):
elements_of_header = col_name.split('_')
new_title = elements_of_header[-1] + "_" + elements_of_header[0]
return new_title
An alternative to the other answer. Using your function and DataFrame.rename
import pandas as pd
def rejig_col_names(columns):
elements_of_header = columns.split('_')
new_title = elements_of_header[-1] + "_" + elements_of_header[0]
return new_title
data = {
'A_B': [1, 2, 3],
'C_D': [4, 5, 6],
}
df = pd.DataFrame(data)
df.rename(rejig_col_names, axis='columns', inplace=True)
print(df)
str.replace is also an option via swapping capture groups:
Sample input borrowed from ScottBoston
df = pd.DataFrame(data=[['1', '2'], ['3', '4']], columns=['AH_PH', 'AH_AS'])
Then Capture everything before and after the '_' and swap capture group 1 and 2.
df.columns = df.columns.str.replace(r'^(.*)_(.*)$', r'\2_\1', regex=True)
PH_AH AS_AH
0 1 2
1 3 4

Column in DataFrame isn't recognised. Keyword Error: 'Date'

I'm in the initial stages of doing some 'machine learning'.
I'm trying to create a new data frame and one of the columns doesn't appear to be recognised..?
I've loaded an Excel file with 2 columns (removed the index). All fine.
Code:
df = pd.read_excel('scores.xlsx',index=False)
df=df.rename(columns=dict(zip(df.columns,['Date','Amount'])))
df.index=df['Date']
df=df[['Amount']]
#creating dataframe
data = df.sort_index(ascending=True, axis=0)
new_data = pd.DataFrame(index=range(0,len(df)),columns=['Date','Amount'])
for i in range(0,len(data)):
new_data['Date'][i] = data['Date'][i]
new_data['Amount'][i] = data['Amount'][i]
The error:
KeyError: 'Date'
Not really sure what's the problem here.
Any help greatly appreciated
I think in line 4 you reduce your dataframe to just one column "Amount"
To add to #Grzegorz Skibinski's answer, the problem is after line 4, there is no longer a 'Date' column. The Date column was assigned to the index and removed, and while the index has a name "Date", you can't use 'Date' as a key to get the index - you have to use data.index[i] instead of data['Date'][i].
It seems that you have an error in the formatting of your Date column.
To check that you don't have an error on the name of the columns you can print the columns names:
import pandas as pd
# create data
data_dict = {}
data_dict['Fruit '] = ['Apple', 'Orange']
data_dict['Price'] = [1.5, 3.24]
# create dataframe from dict
df = pd.DataFrame.from_dict(data_dict)
# Print columns names
print(df.columns.values)
# Print "Fruit " column
print(df['Fruit '])
This code outputs:
['Fruit ' 'Price']
0 Apple
1 Orange
Name: Fruit , dtype: object
We clearly see that the "Fruit " column as a trailing space. This is an easy mistake to do, especially when using excel.
If you try to call "Fruit" instead of "Fruit " you obtain the error you have:
KeyError: 'Fruit'

concat the strings of one column based on condition on other column

I have a data frame that I want to remove duplicates on column named "sample" and the add string information in gene and status columns to new column as shown in the attached pics.
Thank you so much in advance
below is the modified version of data frame.where gene in rows are replaced by actual gene names
Here, df is your Pandas DataFrame.
def new_1(g):
return ','.join(g.gene)
def new_2(g):
return ','.join(g.gene + '-' + g.status)
new_1_data = df.groupby("sample").apply(new_1).to_frame(name="new_1")
new_2_data = df.groupby("sample").apply(new_2).to_frame(name="new_2")
new_data = pd.merge(new_1_data, new_2_data, on="sample")
new_df = pd.merge(df, new_data, on="sample").drop_duplicates("sample")
If you wish to have "sample" as a column instead of an index, then add
new_df = new_df.reset_index(drop=True)
Lastly, as you did not specify which of the original rows of duplicates to retain, I simply use the default behavior of Pandas and drop all but the first occurrence.
Edit
I converted your example to the following CSV file (delimited by ',') which I will call "data.csv".
sample,gene,status
ppar,p53,gain
ppar,gata,gain
ppar,nb,loss
srty,nf1,gain
srty,cat,gain
srty,cd23,gain
tygd,brac1,loss
tygd,brac2,gain
tygd,ras,loss
I load this data as
# Default delimiter is ','. Pass `sep` argument to specify delimiter.
df = pd.read_csv("data.csv")
Running the code above and printing the dataframe produces the output
sample gene status new_1 new_2
0 ppar p53 gain p53,gata,nb p53-gain,gata-gain,nb-loss
3 srty nf1 gain nf1,cat,cd23 nf1-gain,cat-gain,cd23-gain
6 tygd brac1 loss brac1,brac2,ras brac1-loss,brac2-gain,ras-loss
This is exactly the expected output given in your example.
Note that the left-most column of numbers (0, 3, 6) are the remnants of the index of the original dataframes produced after the merges. When you write this dataframe to file you can exclude it by setting index=False for df.to_csv(...).
Edit 2
I checked the CSV file you emailed me. You have a space after the word "gene" in the header of your CSV file.
Change the first line of your CSV file from
sample,gene ,status
to
sample,gene,status
Also, there are spaces in your entries. If you wish to remove them, you can
# Strip spaces from entries. Only works for string entries
df = df.applymap(lambda x: x.strip())
Might not be the most efficient solution but this should get you there:
samples = []
genes= []
statuses = []
for s in set(df["sample"]):
#grab unique samples
samples.append(s)
#get the genes for each sample and concatenate them
g = df["gene"][df["sample"]==s].str.cat(sep=",")
genes.append(g)
#loop through the genes for the sample and get the statuses
status = ''
for gene in g.split(","):
gene_status = df["status"][(df["sample"] == s) & (df["gene"] == gene)].to_string(index=False)
status += gene
status += "-"
status += gene_status
status += ','
statuses.append(status)
#create new df
new_df = pd.DataFrame({'sample': samples,
'new': genes,
'new1': statuses})

Formatting a specific row of integers to the ssn style

I want to format a specific column of integers to ssn format (xxx-xx-xxxx). I saw that openpyxl has builtin styles. I have been using pandas and wasn't sure if it could do this specific format.
I did see this -
df.iloc[:,:].str.replace(',', '')
but I want to replace the ',' with '-'.
import pandas as pd
df = pd.read_excel('C:/Python/Python37/Files/Original.xls')
df.drop(['StartDate', 'EndDate','EmployeeID'], axis = 1, inplace=True)
df.rename(columns={'CheckNumber': 'W/E Date', 'CheckBranch': 'Branch','DeductionAmount':'Amount'},inplace=True)
df = df[['Branch','Deduction','CheckDate','W/E Date','SSN','LastName','FirstName','Amount','Agency','CaseNumber']]
ssn = (df['SSN'] # the integer column
.astype(str) # cast integers to string
.str.zfill(8) # zero-padding
.pipe(lambda s: s.str[:2] + '-' + s.str[2:4] + '-' + s.str[4:]))
writer = pd.ExcelWriter('C:/Python/Python37/Files/Deductions Report.xlsx')
df.to_excel(writer,'Sheet1')
writer.save()
Your question is a bit confusing, see if this helps:
If you have a column of integers and you want to create a new one made up of strings in SSN (Social Security Number) format. You can try something like:
df['SSN'] = (df['SSN'] # the "integer" column
.astype(int) # the integer column
.astype(str) # cast integers to string
.str.zfill(9) # zero-padding
.pipe(lambda s: s.str[:3] + '-' + s.str[3:5] + '-' + s.str[5:]))
Setup
Social Security numbers are nine-digit numbers using the form: AAA-GG-SSSS
s = pd.Series([111223333, 222334444])
0 111223333
1 222334444
dtype: int64
Option 1
Using zip and numpy.unravel_index:
pd.Series([
'{}-{}-{}'.format(*el)
for el in zip(*np.unravel_index(s, (1000,100,10000)))
])
Option 2
Using f-strings:
pd.Series([f'{i[:3]}-{i[3:5]}-{i[5:]}' for i in s.astype(str)])
Both produce:
0 111-22-3333
1 222-33-4444
dtype: object
I prefer:
df["ssn"] = df["ssn"].astype(str)
df["ssn"] = df["ssn"].str.strip()
df["ssn"] = (
df.ssn.str.replace("(", "")
.str.replace(")", "")
.str.replace("-", "")
.str.replace(" ", "")
.apply(lambda x: f"{x[:3]}-{x[3:5]}-{x[5:]}")
)
This take into account rows that are partially formatted, fully formatted, or not formatted and correctly formats them all.
For Example:
data = [111111111,123456789,"222-11-3333","433-3131234"]
df = pd.DataFrame(data, columns=['ssn'])
Gives you:
Before
After the code you then get:
After

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