There can be a lot of solutions. In the comments of the code block (#) you will find a few links for more information:
import pandas as pd
import numpy as np
import random
import string
k = 5
N = 10
#http://docs.scipy.org/doc/numpy/reference/generated/numpy.random.randint.html
#http://stackoverflow.com/a/2257449/2901002
df = pd.DataFrame({ 'A' : range(1, N + 1 ,1),
    'B' : np.random.randint(k, k + 100 , size=N),
    'C' : pd.Series(random.choice(string.ascii_uppercase) for _ in range(N)) })
print df
#    A   B  C
#0   1  60  O
#1   2  94  L
#2   3  10  W
#3   4  94  X
#4   5  60  O
#5   6  20  K
#6   7  58  Y
#7   8  40  I
#8   9  49  X
#9  10  65  S
Numpy solution:
import pandas as pd
import numpy as np
k = 5
N = 10
alphabet = list('ABCDEFGHIJKLMNOPQRSTUVWXYZ')
#http://docs.scipy.org/doc/numpy/reference/generated/numpy.random.choice.html
df = pd.DataFrame({ 'A' : range(1, N + 1 ,1),
    'B' : np.random.randint(k, k + 100 , size=N),
    'C' : np.random.choice(np.array(alphabet, dtype="|S1"), N) })
print df
#    A    B  C
#0   1   16  U
#1   2   76  X
#2   3  101  N
#3   4   61  F
#4   5   52  J
#5   6   62  A
#6   7   99  L
#7   8   23  N
#8   9   75  D
#9  10   16  Q