pandasでgroupbyしたところにapplyして使う用の関数です

group_apply.py

def dup(df, columns=['columns_name']):
  return df.duplicated(subset=columns)

def dup_count(df, columns=['columns_name']):
  return df.duplicated(subset=columns).value_counts()

def vcount(df):
  return df.value_counts()

def count(df):
  return df.count()

def count_max(df):
  return df.value_counts().max()

def diff(df):
  return df.count() - df.value_counts().max()