Is there a function to write certain values of a dataframe to a .txt file in Python?

Question

I have a dataframe as follows:

Index A B C D E F
1     0 0 C 0 E 0 
2     A 0 0 0 0 F
3     0 0 0 0 E 0
4     0 0 C D 0 0 
5     A B 0 0 0 0

Basically I would like to write the dataframe to a txt file, such that every row consists of the index and the subsequent column name only, excluding the zeroes.

For example:

txt file

1 C E 
2 A F 
3 E 
4 C D 
5 A B

The dataset is quite big, about 1k rows, 16k columns. Is there any way I can do this using a function in Pandas?

Asked By: Radhika

||

Source

Answer 1

Take a matrix vector multiplication between the boolean matrix generated by "is this entry "0" or not" and the columns of the dataframe, and write it to a text file with to_csv (thanks to @Andreas’ answer!):

df.ne("0").dot(df.columns + " ").str.rstrip().to_csv("text_file.txt")

where we right strip the spaces at the end due to the added " " to the last entries.

If you don’t want the name Index appearing in the text file, you can chain a rename_axis(index=None) to get rid of it i.e.,

df.ne("0").dot(df.columns + " ").str.rstrip().rename_axis(index=None)

and then to_csv as above.

Answered By: Mustafa Aydın

Answer 2

You can try this (replace ‘0’ with 0 if that are numeric 0 instead of string 0):

# Credits to Pygirl, made the code even better.
df.set_index('Index', inplace=True)
df = df.replace('0',np.nan)
df.stack().groupby(level=0).apply(list)

# Out[79]: 
# variable
# 0    [C, E]
# 1    [A, F]
# 2       [E]
# 3    [C, D]
# 4    [A, B]
# Name: value, dtype: object

For the writing to text, you can use pandas as well:

df.to_csv('your_text_file.txt')

Answered By: Andreas

Answer 3

You could replace string ‘0’ with empty string '', then so some string-list-join manipulation to get the final results. Finally append each line into a text file. See code:

df = pd.DataFrame([
    ['0','0','C','0','E','0'],
    ['A','0','0','0','0','F'],
    ['0','0','0','0','E','0'],
    ['0','0','C','D','0','0'],
    ['A','B','0','0','0','0']], columns=['A','B','C','D','E','F']
)
df = df.replace('0', '')

logfile = open('test.txt', 'a')
for i in range(len(df)):
    temp = ''.join(list(df.loc[i,:]))
    logfile.write(str(i+1) + ' ' + ' '.join(list(temp)) + 'n')
logfile.close()

Output test.txt

1 C E
2 A F
3 E
4 C D
5 A B

Answered By: perpetualstudent

Is there a function to write certain values of a dataframe to a .txt file in Python?

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