Ben Chuanlong Du's Blog

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User-defined Function (UDF) in PySpark

Tips and Traps

  1. The easist way to define a UDF in PySpark is to use the @udf tag, and similarly the easist way to define a Pandas UDF in PySpark is to use the @pandas_udf tag. Pandas UDFs are preferred to UDFs for server reasons. First, pandas UDFs are typically much faster than UDFs. Second, pandas UDFs are more flexible than UDFs on parameter passing. Both UDFs and pandas UDFs can take multiple columns as parameters. In addition, pandas UDFs can take a DataFrame as parameter (when passed to the apply

Regular Expression Equivalent

  1. The order of precedence of operators in POSIX extended regular expression is as follows.

    1. Collation-related bracket symbols [==], [::], [..]
    2. Escaped characters \
    3. Character set (bracket expression) []
    4. Grouping ()
    5. Single-character-ERE duplication *, +, ?, {m,n}
    6. Concatenation
    7. Anchoring ^, $
    8. Alternation |

  2. Some regular expression patterns are defined using a single leading backslash, e.g., \s, \b, etc. However, since special …

Install Python Packages Behind Firewall

It is recommended that you use pip to install Python packages.

  1. If you don't already know the proxy in use (in your company), read the post Find out Proxy in Use to figure it out.

  2. Set proxy environment variables.

    set http_proxy=http://user:password@proxy_ip:port
set https_proxy=https://user …