how many frames in dataframe python count code example

Example 1: python - count total numeber of row in a dataframe

# Option 1
df.A.count()
# Option 2
df['A'].count()
# Option 3
number_of_rows = len(df) 
# Option 4
df.count()

Example 2: python count variable and put the count in a column of data frame

df['freq'] = df.groupby('myvar')['myvar'].transform('count')