bash

1. Loop through lines in a file

    while read p; do
      echo "$p"
    done <peptides.txt
   

python

1. handle exceptions

    while True:
    ...     try:
    ...         x = int(input("Please enter a number: "))
    ...         break
    ...     except ValueError:
    ...         print("Oops!  That was no valid number.  Try again...") ## string
   

2. replace() method

    txt = "I like bananas"
   
    x = txt.replace("bananas", "apples")
   

list

1. list comprehension

    [v for v in my_list for _ in range(3)] ## dictionary
   

2. delete a key from a dictionary

    a_dict.pop('John')
   

3. subset a dictionary

    myDict = {key:val for key, val in myDict.items() if val != 42}
   

pandas

1. split a column into multiple

    user_df['name'].str.split(pat = ' ', expand = True)
   

2. drop duplicated rows

    df.drop_duplicates()
   

3. selected rows based on a condition

    new = df[~df.filter(regex='^node').isin([3,7,18]).any(1)]
    df.drop(df[df.score < 50].index)
   

R

1. subset data to contain only columns whose names match a condition

    df[ , grepl( "ABC" , names( df ) ) ]	
   

2. vectorize any funciton

    vectorized_substr <- base::Vectorize(substr)
   

ggplot2

1. beta-diversity

    p2 = plot_ordination(GP1, GP.ord, type="samples", color="SampleType", shape="human") 
    p2 + geom_polygon(aes(fill=SampleType)) + geom_point(size=5) + ggtitle("samples")
   

2. change default shape types

    scale_shape_manual(values=c(3, 16))