Pandas dataframe: truncate string fields

Question

I have a dataframe and would like to truncate each field to up to 20 characters. I\'ve been naively trying the following:

df = df.astype(str).apply(lambda x:         


        

Answer 1

I think need str for indexing with str:

df = df.astype(str).apply(lambda x: x.str[:20])

Sample:

df = pd.DataFrame({'A':[1,2,3],
                   'B':[4,5,6],
                   'C':[7,8,9],
                   'D':[1,3,5],
                   'E':[5,3,6],
                   'F':[7,4,3]}) * 1000

print (df)
      A     B     C     D     E     F
0  1000  4000  7000  1000  5000  7000
1  2000  5000  8000  3000  3000  4000
2  3000  6000  9000  5000  6000  3000

df = df.astype(str).apply(lambda x: x.str[:2])
print (df)
    A   B   C   D   E   F
0  10  40  70  10  50  70
1  20  50  80  30  30  40
2  30  60  90  50  60  30

Another solution with applymap:

df = df.astype(str).applymap(lambda x: x[:2])
print (df)
    A   B   C   D   E   F
0  10  40  70  10  50  70
1  20  50  80  30  30  40
2  30  60  90  50  60  30

Problem of your solution is if x[:20] select only first 20 rows in each column.

You can test it by custom function:

def f(x):
    print (x)
    print (x[:2])

df = df.astype(str).apply(f)
print (df)