Python

Loops

Files in a directory

import os

directory = os.fsencode(directory_in_str)

for file in os.listdir(directory):
    filename = os.fsdecode(file)
    if filename.endswith(".txt"): 
        print("Found a text file"))
        continue
    else:
        continue

Lines in a file

file = open('input.txt','r')
for line in file:
    print(line)

Pandas

Conditionally create a column based on another column.

source

def function(row):
    if row['A'] == row['B']:
        val = 0
    elif row['A'] > row['B']:
        val = 1
    else:
        val = -1
    return val
df['C'] = df.apply(f, axis=1)

Fill null values

df = df.fillna('')

Rename columns

df = df.rename(columns={'old_name':'new_name'})

Remove columns

df = df.remove(columns=['column_a', 'column_b'])

Types

Check if string is a valid integer

'14'.isdigit()

Lists

Test is one list is in another list

any(map(lambda v: v in list2, list1))