Write a pandas dataframe with different datatypes left aligned into a txt-file

Question

Having the following dataframe:

import pandas as pd

data = {'Column1': ['1e10', '123.1105', '0.5e-2', '0'],
        'Column2': ['String1', 'String3', 101, 'String4']}
df = pd.DataFrame(data)

I want to write it into a txt-file looking like that, where the spaces are really just spaces (no tabs etc.) and every column is aligned left:

------- Data --------
Column1  Column2
1e10     String1
123.1105 String3
0.5e-2   101
0        String4

The closest I have gotten to this is:

from tabulate import tabulate

# Format dataframe into table
table_content = tabulate(df.values.tolist(),tablefmt="plain")

# Write the txt-file
with open("example.txt", "w") as file:
    file.write("------- Data --------")
    file.write(table_content)

Where the output is:

------- Data --------
Column1  Column2
  1e+10  String1
123.111  String3
  0.005  101
  0      String4

The first column though should really be treated as strings: aligned to the left and in the format as specified (this is input for another program that requests it like that). Is there a way to do that efficiently?

Answer 1

You could convert the first column into strings and then use str.ljust:

import pandas as pd

data = {
    'Column1': ['1e10', '123.1105', '0.5e-2', '0'],
    'Column2': ['String1', 'String3', 101, 'String4']
}
df = pd.DataFrame(data)
df = df.astype(str)
max_widths = [max(len(str(col)), *df[col].astype(str).apply(len)) for col in df.columns]
with open('example.txt', 'w') as file:
  file.write('------- Data --------\n')
  header = ' '.join(
      col.ljust(max_widths[i]) for i, col in enumerate(df.columns))
  file.write(header + '\n')
  for index, row in df.iterrows():
    row_str = ' '.join(
        str(value).ljust(max_widths[i]) for i, value in enumerate(row))
    file.write(row_str + '\n')

Output:

------- Data --------
Column1  Column2
1e10     String1
123.1105 String3
0.5e-2   101    
0        String4