I am getting syntax error with the .merge() Pandas function.
What am I doing wrong and how can I fix it?
Below is a snippet of my code;
df2 = df2.merge(df1[list('col1','col2'], on ='ABC')
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5 Answers
You need to use a string formatting for that:
>>> for n in (9, 99, 999, 9999):
... print(f"{n:0>4}")
...
0009
0099
0999
9999
Comments
str.zfill(x) will put x zeroes before any string
If you'd rather use string formatting, f'{str:0x}' also works.
P.S. Don't name your strings str as it overloads the str class
2 Comments
gmds
I think this is more Pythonic than string formatting, especially C-style formatting.
CryptoFool
I consider this less readable. I do prefer the new string formatting style to the old 'C style'.
Using str.zfill(width):
The method zfill() pads string on the left with zeros to fill width.
width − This is final width of the string. This is the width which we would get after filling zeros.
id = [6, 77, 888, 9999]
print([str(x).zfill(4) for x in id])
OUTPUT:
['0006', '0077', '0888', '9999']
EDIT:
To convert the column values in a column using list-comprehension:
import pandas as pd
df = pd.DataFrame({'un-padded':[6, 77, 888, 9999]})
df['padded'] = [str(x).zfill(4) for x in df['un-padded']]
print(df)
OUTPUT:
un-padded padded
0 6 0006
1 77 0077
2 888 0888
3 9999 9999
3 Comments
Pradeep
I have one column containing thousands of such ID and need to insert a new column using zfill(). How can I do that?
DirtyBit
@Pradeep added an edit for it :)
Pradeep
This is my first python code so I might be asking too silly things. import csv with open('example.csv') as csvfile: readCSV = csv.reader(csvfile, delimiter=',') with open ('new_'+csvfile, 'w') as output: writer = csv.writer(output, delimiter =',') writer.writerow(next(reader) + ['New-column'] After this I need to use zfill to insert new values which are there in xyz column. Could you help me to do this?
You will have to treat it as a string value, as numeric values can't have leading zeros. To create a 0-padded string of length 4, you can do this:
v = 4
print("{:04d}".format(v))
or the older style:
v = 4
print("%04d" % v)
Result either way:
0004
Comments
String formatting is the answer.
print('%04d' % 4)
0004
print('%04d' % 43)
0043
