英文:
Python Polars find the length of a string in a dataframe
问题
我尝试在Polars中计算字符串中字母的数量。我可能可以只使用apply方法并获取len(Name)。但是，我想知道是否有Polars特定的方法？
import polars as plmydf = pl.DataFrame({"start_date": ["2020-01-02", "2020-01-03", "2020-01-04"],"Name": ["John", "Joe", "James"]})print(mydf)│start_date ┆ Name ││ --- ┆ --- ││ str ┆ str │╞════════════╪═══════╡│ 2020-01-02 ┆ John ││ 2020-01-03 ┆ Joe ││ 2020-01-04 ┆ James │
最终John将有5个字母，Joe将有3个字母，James将有5个字母。
我认为类似于以下内容可能适用于Pandas的等效代码：
# 假设这是一个Pandas DataFramemydf['count'] = mydf['Name'].str.len()# Polars等效 - 错误mydf = mydf.with_columns(pl.col('Name').str.len().alias('count'))
英文:
I am trying to count the number of letters in a string in Polars.
I could probably just use an apply method and get the len(Name).
However, I was wondering if there is a polars specific method?
import polars as plmydf = pl.DataFrame({"start_date": ["2020-01-02", "2020-01-03", "2020-01-04"],"Name": ["John", "Joe", "James"]})print(mydf)│start_date ┆ Name ││ --- ┆ --- ││ str ┆ str │╞════════════╪═══════╡│ 2020-01-02 ┆ John ││ 2020-01-03 ┆ Joe ││ 2020-01-04 ┆ James │
In the end John would have 5, Joe would be 3 and James would be 5
I thought something like below might work based on the Pandas equivalent
# Assume that its a Pandas Dataframemydf['count'] = mydf ['Name'].str.len()# Polars equivalent - ERRORsmydf = mydf.with_columns(pl.col('Name').str.len().alias('count'))
答案1
得分: 2
你可以使用以下方法：
mydf.with_columns([pl.col("Name").str.lengths().alias("len")])
┌────────────┬───────┬─────┐│ start_date ┆ Name ┆ len ││ --- ┆ --- ┆ --- ││ str ┆ str ┆ u32 │╞════════════╪═══════╪═════╡│ 2020-01-02 ┆ John ┆ 4 ││ 2020-01-03 ┆ Joe ┆ 3 ││ 2020-01-04 ┆ James ┆ 5 │└────────────┴───────┴─────┘
英文:
You can use
.str.lengths()that counts number of bytes in the UTF8 string (doc) - faster.str.n_chars()that counts number of characters (doc)
mydf.with_columns([pl.col("Name").str.lengths().alias("len")])
┌────────────┬───────┬─────┐│ start_date ┆ Name ┆ len ││ --- ┆ --- ┆ --- ││ str ┆ str ┆ u32 │╞════════════╪═══════╪═════╡│ 2020-01-02 ┆ John ┆ 4 ││ 2020-01-03 ┆ Joe ┆ 3 ││ 2020-01-04 ┆ James ┆ 5 │└────────────┴───────┴─────┘
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论