pandas replace column values

# 1. Replace a single value with a new value for an individual DataFrame column:
df['column name'] = df['column name'].replace(['old value'],'new value')

# 2. Replace multiple values with a new value for an individual DataFrame column:
df['column name'] = df['column name'].replace(['1st old value','2nd old value',...],'new value')

# 3. Replace multiple values with multiple new values for an individual DataFrame column:
df['column name'] = df['column name'].replace(['1st old value','2nd old value',...],['1st new value','2nd new value',...])

# 4. Replace a single value with a new value for an entire DataFrame:
df = df.replace(['old value'],'new value')

In [41]:
df.loc[df['First Season'] > 1990, 'First Season'] = 1
df

Out[41]:
                 Team  First Season  Total Games
0      Dallas Cowboys          1960          894
1       Chicago Bears          1920         1357
2   Green Bay Packers          1921         1339
3      Miami Dolphins          1966          792
4    Baltimore Ravens             1          326
5  San Franciso 49ers          1950         1003

df['column'] = df['column'].str.replace(',','-')
df