How to combine DataFame column data and fixed text string - python

I want to combine 4 columns within a larger DataFrame with a custom (space) delimiter (which I have done with the code below) but then I want to add a fixed string to the start and end of each concatenation.
The columns are pairs of X & Y coordinates, but they can be dealt with as str for this purpose (once I've trimmed to 3 decimal places).
I have found many options on this website for joining the columns, but none to join columns and a consistent fixed string.The lazy way would be for me to just make two more DataFrame columns, one for the start, one for the end, and cat everything. Is there a more sophisticated way to do it?
import pandas as pd
from pandas import DataFrame
import numpy as np
def str_join(df, sep, *cols):
from functools import reduce
return reduce (lambda x,y: x.astype(str).str.cat(y.astype(str), sep=sep),
[df[col] for col in cols])
data= pd.read_csv('/Users/XXXXXX/Desktop/Lines.csv')
df=pd.DataFrame(data, columns=['Name','SOLE','SOLN','EOLE','EOLN','EOLKP','Wind','Wave'])
df['SOLE']=round(df['SOLE'],3)
df['SOLN']=round(df['SOLN'],3)
df['EOLE']=round(df['EOLE'],3)
df['EOLN']=round(df['EOLN'],3)
df['WKT']=str_join(df,' ','SOLE','SOLN','EOLE','EOLN')
df.to_csv('OutLine.csv') #turn on to create output file
which gives me.
WKT
476912.131 6670122.285 470329.949 6676260.271
What I want to do is add '(LINESTRING ' to the start of each concatenation and ')' to the end of each to give me.
WKT
(LINESTRING 476912.131 6670122.285 470329.949 6676260.271 )

You could also create a collection of the columns you want to export, do a quick data type format, and apply a join.
target_cols = ['SOLE','SOLN','EOLE','EOLN',]
# Make sure to use along axis 1 (columns) because default is 0
# Also, if you're on Python 3.6+, I think you can use f-strings to format your floats.
df['WKT'] = df[target_cols].apply(lambda x: '(LINESTRING ' + ' '.join(f"{i:.3f}" for i in x) + ')', axis=1)
result:
In [0]: df.iloc[:,-3:]
Out [0]:
Wind Wave WKT
0 wind1 wave1 (LINESTRING 476912.131 6670122.285 470329.949 ...
** Sorry, I'm using Spyder, which is a terminal output miser. Here's a printout of 'WKT'
In [1]: print(df['WKT'].values)
Out [1]: ['(LINESTRING 476912.131 6670122.285 470329.949 6676260.271)']
* **EDIT: To add a comma after 'SOLN', we could use an alternative route:
target_cols = ['SOLE','SOLN','EOLE','EOLN',]
# Format strings in advance
# Set comma_col to our desired column name. This could also be a tuple for multiple names, then replace `==` with `in` in the loop below.
comma_col = 'SOLN'
# To find the last column, which doesn't need a space here, we just select the last value from our list. I did it this way in case our list order doesn't match the dataframe order.
last_col = df[target_cols].columns.values.tolist()[-1]
# Traditional if-then method
for col in df[target_cols]:
if col == comma_col:
df[col] = df[col].apply(lambda x: f"{x:.3f}" + ",") # Explicit comma
elif col == last_col:
df[col] = df[col].apply(lambda x: f"{x:.3f}")
else:
df[col] = df[col].apply(lambda x: f"{x:.3f}" + " ") # Explicit whitespace
# Adding our 'WKT' column as before, but the .join() portion doesn't have a space in it now.
df['WKT'] = df[target_cols].apply(lambda x: '(LINESTRING ' + ''.join(i for i in x) + ')', axis=1)
Finally:
In [0]: print(df['WKT'][0])
Out [0]: (LINESTRING 476912.131 6670122.286,470329.950 6676260.271)

Your function already looks good just you need to add few things:
def str_join(df, sep, *cols):
# All cols must be numeric to use df[col].round(3)
from functools import reduce
return reduce (lambda x,y: 'LINESTRING ' + x.astype(str).str.cat(y.astype(str) + ' )', sep=sep),
[df[col].round(3) for col in cols])

use it this way
df['new']='LINESTRING'
df['WKT']=pd.concat([df['new'],df['SOLE'],df['SOLN'],df['EOLE'],df['EOLN']])

Related

Python dataframe : strip part of string, on each column row, if it is in specific format [duplicate]

I have read some pricing data into a pandas dataframe the values appear as:
$40,000*
$40000 conditions attached
I want to strip it down to just the numeric values.
I know I can loop through and apply regex
[0-9]+
to each field then join the resulting list back together but is there a not loopy way?
Thanks
You could use Series.str.replace:
import pandas as pd
df = pd.DataFrame(['$40,000*','$40000 conditions attached'], columns=['P'])
print(df)
# P
# 0 $40,000*
# 1 $40000 conditions attached
df['P'] = df['P'].str.replace(r'\D+', '', regex=True).astype('int')
print(df)
yields
P
0 40000
1 40000
since \D matches any character that is not a decimal digit.
You could use pandas' replace method; also you may want to keep the thousands separator ',' and the decimal place separator '.'
import pandas as pd
df = pd.DataFrame(['$40,000.32*','$40000 conditions attached'], columns=['pricing'])
df['pricing'].replace(to_replace="\$([0-9,\.]+).*", value=r"\1", regex=True, inplace=True)
print(df)
pricing
0 40,000.32
1 40000
You could remove all the non-digits using re.sub():
value = re.sub(r"[^0-9]+", "", value)
regex101 demo
You don't need regex for this. This should work:
df['col'] = df['col'].astype(str).convert_objects(convert_numeric=True)
In case anyone is still reading this. I'm working on a similar problem and need to replace an entire column of pandas data using a regex equation I've figured out with re.sub
To apply this on my entire column, here's the code.
#add_map is rules of replacement for the strings in pd df.
add_map = dict([
("AV", "Avenue"),
("BV", "Boulevard"),
("BP", "Bypass"),
("BY", "Bypass"),
("CL", "Circle"),
("DR", "Drive"),
("LA", "Lane"),
("PY", "Parkway"),
("RD", "Road"),
("ST", "Street"),
("WY", "Way"),
("TR", "Trail"),
])
obj = data_909['Address'].copy() #data_909['Address'] contains the original address'
for k,v in add_map.items(): #based on the rules in the dict
rule1 = (r"(\b)(%s)(\b)" % k) #replace the k only if they're alone (lookup \
b)
rule2 = (lambda m: add_map.get(m.group(), m.group())) #found this online, no idea wtf this does but it works
obj = obj.str.replace(rule1, rule2, regex=True, flags=re.IGNORECASE) #use flags here to avoid the dictionary iteration problem
data_909['Address_n'] = obj #store it!
Hope this helps anyone searching for the problem I had. Cheers

Split and Join Series in Pandas

I have two series in the dataframe below. The first is a string which will appear in the second, which will be a url string. What I want to do is change the first series by concatenating on extra characters, and have that change applied onto the second string.
import pandas as pd
#import urlparse
d = {'OrigWord' : ['bunny', 'bear', 'bull'], 'WordinUrl' : ['http://www.animal.com/bunny/ear.html', 'http://www.animal.com/bear/ear.html', 'http://www.animal.com/bull/ear.html'] }
df = pd.DataFrame(d)
def trial(source_col, dest_col):
splitter = dest_col.str.split(str(source_col))
print type(splitter)
print splitter
res = 'angry_' + str(source_col).join(splitter)
return res
df['Final'] = df.applymap(trial(df.OrigWord, df.WordinUrl))
I'm trying to find the string from the source_col, then split on that string in the dest_col, then effect that change on the string in dest_col. Here I have it as a new series called Final but I would rather inplace. I think the main issue are the splitter variable, which isn't working and the application of the function.
Here's how result should look:
OrigWord WordinUrl
angry_bunny http://www.animal.com/angry_bunny/ear.html
angry_bear http://www.animal.com/angry_bear/ear.html
angry_bull http://www.animal.com/angry_bull/ear.html
apply isn't really designed to apply to multiple columns in the same row. What you can do is to change your function so that it takes in a series instead and then assigns source_col, dest_col to the appropriate value in the series. One way of doing it is as below:
def trial(x):
source_col = x["OrigWord"]
dest_col = x['WordinUrl' ]
splitter = str(dest_col).split(str(source_col))
res = splitter[0] + 'angry_' + source_col + splitter[1]
return res
df['Final'] = df.apply(trial,axis = 1 )
here is an alternative approach:
df['WordinUrl'] = (df.apply(lambda x: x.WordinUrl.replace(x.OrigWord,
'angry_' + x.OrigWord), axis=1))
In [25]: df
Out[25]:
OrigWord WordinUrl
0 bunny http://www.animal.com/angry_bunny/ear.html
1 bear http://www.animal.com/angry_bear/ear.html
2 bull http://www.animal.com/angry_bull/ear.html
Instead of using split, you can use the replace method to prepend the angry_ to the corresponding source:
def trial(row):
row.WordinUrl = row.WordinUrl.replace(row.OrigWord, "angry_" + row.OrigWord)
row.OrigWord = "angry_" + row.OrigWord
return row
df.apply(trial, axis = 1)
OrigWord WordinUrl
0 angry_bunny http://www.animal.com/angry_bunny/ear.html
1 angry_bear http://www.animal.com/angry_bear/ear.html
2 angry_bull http://www.animal.com/angry_bull/ear.html

pandas to_csv split some rows in 2 lines

i have a problem with pandas.to_csv
pandas dataframe work correctly and pd.to_excel work well too.
when i try to use .to_csv some rows splitted in two (i see it in wordpad and excel)
for example:
line 1: provincia;comune;Ragione sociale;indirizzo;civico;destinazione;sup_coperta
line2: AR;CHIUSI DELLA VERNA;ex sacci;LOC. CORSALONE STRADA REGIONALE
line3: 71;;SITO DISMESSO;
my code toscana.to_csv("toscana.csv", index = False, encoding = "utf-8", sep=";")
EDIT: i add some line with the problem
(thx to all for the comments!)
`
how i can remove line breaks in values? I found \r in a cell splitted in 2 csv lines: Out[17]: u'IMPIANTI SPORTIVI: CIRCOLO CULTURALE RICREATIVO \rPESTELLO'
i solve with
def replace(x):
if type(x) == str or type(x) == unicode:
x = x.replace('\r', '')
else:
x = x[0].replace('\r', '')
return x
toscana["indirizzo"] = toscana["indirizzo"].map(lambda x: x.replace('"', ''))
toscana["indirizzo"] = toscana["indirizzo"].map(lambda x: replace(x))
toscana["Ragione sociale"] = toscana["Ragione sociale"].map(lambda x: x.replace('"', ''))
toscana["Ragione sociale"] = toscana["Ragione sociale"].map(lambda x: replace(x))
there is smarter methods to do it?
You can use the Pandas Replace method to achieve this rather than creating a new function.
Pandas Replace Method
It includes regex so you can include expressions in the replace such as | for Or
In the example we will use regex=True and replace the \\ with a \ using regex
adding inplace = True will change the value without adding / removing any data from the position in the table.
r"\\t|\\n|\\r" is the same as "\\t" or "\\n" or "\\r" and we replace with the single \
df.replace(to_replace=[r"\\t|\\n|\\r", "\t|\n|\r"], value=["",""], regex=True, inplace=True)

Pythonic/efficient way to strip whitespace from every Pandas Data frame cell that has a stringlike object in it

I'm reading a CSV file into a DataFrame. I need to strip whitespace from all the stringlike cells, leaving the other cells unchanged in Python 2.7.
Here is what I'm doing:
def remove_whitespace( x ):
if isinstance( x, basestring ):
return x.strip()
else:
return x
my_data = my_data.applymap( remove_whitespace )
Is there a better or more idiomatic to Pandas way to do this?
Is there a more efficient way (perhaps by doing things column wise)?
I've tried searching for a definitive answer, but most questions on this topic seem to be how to strip whitespace from the column names themselves, or presume the cells are all strings.
Stumbled onto this question while looking for a quick and minimalistic snippet I could use. Had to assemble one myself from posts above. Maybe someone will find it useful:
data_frame_trimmed = data_frame.apply(lambda x: x.str.strip() if x.dtype == "object" else x)
You could use pandas' Series.str.strip() method to do this quickly for each string-like column:
>>> data = pd.DataFrame({'values': [' ABC ', ' DEF', ' GHI ']})
>>> data
values
0 ABC
1 DEF
2 GHI
>>> data['values'].str.strip()
0 ABC
1 DEF
2 GHI
Name: values, dtype: object
We want to:
Apply our function to each element in our dataframe - use applymap.
Use type(x)==str (versus x.dtype == 'object') because Pandas will label columns as object for columns of mixed datatypes (an object column may contain int and/or str).
Maintain the datatype of each element (we don't want to convert everything to a str and then strip whitespace).
Therefore, I've found the following to be the easiest:
df.applymap(lambda x: x.strip() if type(x)==str else x)
When you call pandas.read_csv, you can use a regular expression that matches zero or more spaces followed by a comma followed by zero or more spaces as the delimiter.
For example, here's "data.csv":
In [19]: !cat data.csv
1.5, aaa, bbb , ddd , 10 , XXX
2.5, eee, fff , ggg, 20 , YYY
(The first line ends with three spaces after XXX, while the second line ends at the last Y.)
The following uses pandas.read_csv() to read the files, with the regular expression ' *, *' as the delimiter. (Using a regular expression as the delimiter is only available in the "python" engine of read_csv().)
In [20]: import pandas as pd
In [21]: df = pd.read_csv('data.csv', header=None, delimiter=' *, *', engine='python')
In [22]: df
Out[22]:
0 1 2 3 4 5
0 1.5 aaa bbb ddd 10 XXX
1 2.5 eee fff ggg 20 YYY
The "data['values'].str.strip()" answer above did not work for me, but I found a simple work around. I am sure there is a better way to do this. The str.strip() function works on Series. Thus, I converted the dataframe column into a Series, stripped the whitespace, replaced the converted column back into the dataframe. Below is the example code.
import pandas as pd
data = pd.DataFrame({'values': [' ABC ', ' DEF', ' GHI ']})
print ('-----')
print (data)
data['values'].str.strip()
print ('-----')
print (data)
new = pd.Series([])
new = data['values'].str.strip()
data['values'] = new
print ('-----')
print (new)
Here is a column-wise solution with pandas apply:
import numpy as np
def strip_obj(col):
if col.dtypes == object:
return (col.astype(str)
.str.strip()
.replace({'nan': np.nan}))
return col
df = df.apply(strip_obj, axis=0)
This will convert values in object type columns to string. Should take caution with mixed-type columns. For example if your column is zip codes with 20001 and ' 21110 ' you will end up with '20001' and '21110'.
This worked for me - applies it to the whole dataframe:
def panda_strip(x):
r =[]
for y in x:
if isinstance(y, str):
y = y.strip()
r.append(y)
return pd.Series(r)
df = df.apply(lambda x: panda_strip(x))
I found the following code useful and something that would likely help others. This snippet will allow you to delete spaces in a column as well as in the entire DataFrame, depending on your use case.
import pandas as pd
def remove_whitespace(x):
try:
# remove spaces inside and outside of string
x = "".join(x.split())
except:
pass
return x
# Apply remove_whitespace to column only
df.orderId = df.orderId.apply(remove_whitespace)
print(df)
# Apply to remove_whitespace to entire Dataframe
df = df.applymap(remove_whitespace)
print(df)

pandas applying regex to replace values

I have read some pricing data into a pandas dataframe the values appear as:
$40,000*
$40000 conditions attached
I want to strip it down to just the numeric values.
I know I can loop through and apply regex
[0-9]+
to each field then join the resulting list back together but is there a not loopy way?
Thanks
You could use Series.str.replace:
import pandas as pd
df = pd.DataFrame(['$40,000*','$40000 conditions attached'], columns=['P'])
print(df)
# P
# 0 $40,000*
# 1 $40000 conditions attached
df['P'] = df['P'].str.replace(r'\D+', '', regex=True).astype('int')
print(df)
yields
P
0 40000
1 40000
since \D matches any character that is not a decimal digit.
You could use pandas' replace method; also you may want to keep the thousands separator ',' and the decimal place separator '.'
import pandas as pd
df = pd.DataFrame(['$40,000.32*','$40000 conditions attached'], columns=['pricing'])
df['pricing'].replace(to_replace="\$([0-9,\.]+).*", value=r"\1", regex=True, inplace=True)
print(df)
pricing
0 40,000.32
1 40000
You could remove all the non-digits using re.sub():
value = re.sub(r"[^0-9]+", "", value)
regex101 demo
You don't need regex for this. This should work:
df['col'] = df['col'].astype(str).convert_objects(convert_numeric=True)
In case anyone is still reading this. I'm working on a similar problem and need to replace an entire column of pandas data using a regex equation I've figured out with re.sub
To apply this on my entire column, here's the code.
#add_map is rules of replacement for the strings in pd df.
add_map = dict([
("AV", "Avenue"),
("BV", "Boulevard"),
("BP", "Bypass"),
("BY", "Bypass"),
("CL", "Circle"),
("DR", "Drive"),
("LA", "Lane"),
("PY", "Parkway"),
("RD", "Road"),
("ST", "Street"),
("WY", "Way"),
("TR", "Trail"),
])
obj = data_909['Address'].copy() #data_909['Address'] contains the original address'
for k,v in add_map.items(): #based on the rules in the dict
rule1 = (r"(\b)(%s)(\b)" % k) #replace the k only if they're alone (lookup \
b)
rule2 = (lambda m: add_map.get(m.group(), m.group())) #found this online, no idea wtf this does but it works
obj = obj.str.replace(rule1, rule2, regex=True, flags=re.IGNORECASE) #use flags here to avoid the dictionary iteration problem
data_909['Address_n'] = obj #store it!
Hope this helps anyone searching for the problem I had. Cheers

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