#Python read csv skip first line how to

Let us first write a simple utility function that takes a line and returns true if it is a comment line i.e. We can use the same idea to read a file line by line and skip initial comment lines. Here, the condition x<5 is true until the 3rd element (6), therefore dropwhile kept dropping the elements until then. Let us see a simple example of itertools’ dropwhile on a list. dropwhile will drop elements until the filtering condition is false. dropwhile can operate on any thing iterable like the file handler and list with filtering condition. Python’s itertools module has a really neat function/iterator called dropwhile. Read line by line and skip lines using itertools’ dropwhile statement # Second while loop to process the rest of the fileģ. # break while statement if it is not a comment line # Skip initial comments that starts with # Then we use a second while loop to read through the rest of the file line be line. The idea here is to read a file line by line with while statement and break the while statement the moment we see the first line without the comment symbol (or without the pattern of interest). Read line by line and skip comment lines using while statementĪ second approach to read a file and the first part of a file based on some conditions is to use while statement. So clearly it is not an efficient approach to read a file and skip comment lines.Ģ. The problem with this approach to skip a few lines is that we check each line of the file and see if it starts with “#”, which can be prohibitively slow if the file is really big. If the line does not start with “#”, we execute the else block. For example, “#comment”.startswith(“#”) will return TRUE. Python string has a nice method “startswith” to check if a string, in this case a line, starts with specific characters.

#Python read csv skip first line how to

How to skip initial comment lines using if statementĪ naive way to read a file and skip initial comment lines is to use “if” statement and check if each line starts with the comment character “#”.

However, the third approach, which uses itertools’ dropwhile to skip lines while reading a file line by line is efficient and elegant. The second approach to skip lines while reading a text file is efficient, but still bit clunky and a bit of a hack. The first approach is a naive approach using if statement and not efficient. You don’t have to know how many lines you want to skip. Here are 3 ways to read a text file line by line Python and skip initial comment lines. The initial few lines of the text file that you want to skip are typically comment or some meta data and starts with some special characters like “#”. Often, you are not interested in initial few lines and want to skip them and work with rest of the file. Reading a text file line by line is one of the common activities you do while dealing with a big text file.