转换pandas DataFrame列的大小写

Question

I have a DataFrame where the case of a particular column is inconsistent and I want to make it consistent:

In [1]: df = pd.DataFrame({"vals":["alpha","Beta","GAMMA"]})

In [2]: df
Out[2]: 
    vals
0  alpha
1   Beta
2  GAMMA

Is there is an easy, pythonic way to replace each value with the str.upper() of the string str ?

Answer 1

你可以做：

df['vals'] = df['vals'].apply(lambda x: x.upper())

Answer 2

This should work for you:

df['vals'] = map(lambda x: x.upper(), df['vals'])

Or even:

df['vals'] = df['vals'].apply(lambda x: x.upper())

---

Ps.: in recent versions you may also:

df['vals'] = df['vals'].str.upper()

Answer 3

You can make the changes inplace directly on your dataframe:

df["vals"].apply(lambda x: x.upper())

Here .upper() will work whether your elements are of type str or unicode .