Column¶

rename¶

df = pl.DataFrame({
    'foo': [1, 2, 3],
    'bar': [6, 7, 8],
    'ham': ['a', 'b', 'c'],
})
df.rename({'foo': 'apple'})
df.rename(lambda col: 'c' + col[1:])

reorder columns¶

https://stackoverflow.com/questions/71353113/polars-how-to-reorder-columns-in-a-specific-order

Do not use Square bracket indexing:

• cannot be parallelized

• cannot be optimized

  df = pl.DataFrame({
      'z': [1, 2],
      'x': ['a', 'b'],
      'y': [True, False],
  })
  
  df.select(['x', 'y', 'z'])
  

create new column conditional on other columns¶

df.with_columns(
    pl.when(pl.col('x') > 0.5).then(0).otherwise(1).alias('y')
)

list of float col to string¶

df.with_columns(
    pl.col('prices')
    .list.eval(pl.element().cast(pl.Utf8))
    .list.join(',')
    .alias('prices')
)