How to ignore the first line of data when processing CSV data

Question

I am asking Python to print the minimum number from a column of CSV data  but the top row is the column number  and I don t want Python to take the top row into account  How can I make sure Python ignores the first line   This is the code so far   import csv  with open  all16 csv    rb   as inf      incsv   csv reader inf      column   1                     datatype   float               data    datatype column  for row in incsv         least value   min data   print least value   Could you also explain what you are doing  not just give the code  I am very very new to Python and would like to make sure I understand everything

User · Answer

The documentation for the Python 3 CSV module provides this example:

with open('example.csv', newline='') as csvfile:
    dialect = csv.Sniffer().sniff(csvfile.read(1024))
    csvfile.seek(0)
    reader = csv.reader(csvfile, dialect)
    # ... process CSV file contents here ...

The Sniffer will try to auto-detect many things about the CSV file. You need to explicitly call its has_header() method to determine whether the file has a header line. If it does, then skip the first row when iterating the CSV rows. You can do it like this:

if sniffer.has_header():
    for header_row in reader:
        break
for data_row in reader:
    # do something with the row

User · Answer

You could use an instance of the csv module s Sniffer class to deduce the format of a CSV file and detect whether a header row is present along with the built-in next   function to skip over the first row only when necessary   import csv  with open  all16 csv    r   newline     as file      has header   csv Sniffer   has header file read 1024       file seek 0     Rewind      reader   csv reader file      if has header          next reader     Skip header row      column   1     datatype   float     data    datatype row column   for row in reader      least value   min data   print least value    Since datatype and column are hardcoded in your example  it would be slightly faster to process the row like this       data    float row 1   for row in reader    Note  the code above is for Python 3 x  For Python 2 x use the following line to open the file instead of what is shown   with open  all16 csv    rb   as file

User · Answer

use csv DictReader instead of csv Reader  If the fieldnames parameter is omitted  the values in the first row of the csvfile will be used as field names  you would then be able to access field values using row  1   etc

User · Answer

Python 3 X  Handles UTF8 BOM   HEADER  It was quite frustrating that the csv module could not easily get the header  there is also a bug with the UTF-8 BOM  first char in file   This works for me using only the csv module   import csv  def read csv self  csv path  delimiter       with open csv path  newline     encoding  utf-8   as f            https   bugs python org issue7185           Remove UTF8 BOM          txt   f read   1          Remove header line      header   txt splitlines    1      lines   txt splitlines   1          Convert to list      csv rows   list csv reader lines  delimiter delimiter        for row in csv rows          value   row INDEX HERE

User · Answer

I would use tail to get rid of the unwanted first line   tail -n  2  INFIL   whatever script py

User · Answer

For me the easiest way to go is to use range      import csv  with open  files filename csv   as I      reader   csv reader I      fulllist   list reader     Starting with data skipping header for item in range 1  len fulllist           Print each row using  item  as the index value     print  fulllist item

User · Answer

The new  pandas  package might be more relevant than  csv   The code below will read a CSV file  by default interpreting the first line as the column header and find the minimum across columns   import pandas as pd  data   pd read csv  all16 csv   data min

User · Answer

Because this is related to something I was doing  I ll share here    What if we re not sure if there s a header and you also don t feel like importing sniffer and other things    If your task is basic  such as printing or appending to a list or array  you could just use an if statement     Let s say there s 4 columns with open  file csv   as csvfile       csvreader   csv reader csvfile    read first line      first line   next csvreader    My headers were just text  You can use any suitable conditional here      if len first line     4            array append first line    Now we ll just iterate over everything else as usual       for row in csvreader            array append row

User · Answer

I would convert csvreader to list  then pop the first element  import csv          with open fileName   r   as csvfile          csvreader   csv reader csvfile          data   list csvreader                  Convert to list         data pop 0                             Removes the first row          for row in data              print row

User · Answer

Python 2 x csvreader next    Return the next row of the reader   s iterable object as a list  parsed according to the current dialect   csv data   csv reader open  sample csv    csv data next     skip first row for row in csv data      print row    should print second row   Python 3 x csvreader   next      Return the next row of the reader   s iterable object as a list  if the object was returned from reader    or a dict  if it is a DictReader instance   parsed according to the current dialect  Usually you should call this as next reader    csv data   csv reader open  sample csv    csv data   next       skip first row for row in csv data      print row    should print second row

User · Answer

You would normally use next incsv  which advances the iterator one row  so you skip the header  The other  say you wanted to skip 30 rows  would be   from itertools import islice for row in islice incsv  30  None         process

User · Answer

just add  1    example below   data   pd read csv   Users xyz Desktop xyxData xyz csv   sep      header None    1       that works for me in iPython

User · Answer

To skip the first line just call   next inf    Files in Python are iterators over lines

User · Answer

Well  my mini wrapper library would do the job as well    gt  gt  gt  import pyexcel as pe  gt  gt  gt  data   pe load  all16 csv   name columns by row 0   gt  gt  gt  min data column 1     Meanwhile  if you know what header column index one is  for example  Column 1   you can do this instead    gt  gt  gt  min data column  Column 1

User · Answer

In a similar use case I had to skip annoying lines before the line with my actual column names  This solution worked nicely  Read the file first  then pass the list to csv DictReader   with open  all16 csv   as tmp        Skip first line  if any      next tmp  None          line num  row      data   dict enumerate csv DictReader tmp

User · Answer

this might be a very old question but with pandas we have a very easy solution import pandas as pd  data pd read csv  all16 csv  skiprows 1  data  column   min    with skiprows 1 we can skip the first row then we can find the least value using data  column   min

User · Answer

Borrowed from python cookbook   A more concise template code might look like this    import csv with open  stocks csv   as f      f csv   csv reader f       headers   next f csv       for row in f csv            Process row

[python] How to ignore the first line of data when processing CSV data?

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