# Problem 1: Encryption # def build_coder(shift): """ Returns a dict that can apply a Caesar cipher to a letter. The cipher is defined by the shift value. Ignores non-letter characters like punctuation and numbers.

shift: -27 < int < 27 returns: dict

Example: >>> build_coder(3) {' ': 'c', 'A': 'D', 'C': 'F', 'B': 'E', 'E': 'H', 'D': 'G', 'G': 'J', 'F': 'I', 'I': 'L', 'H': 'K', 'K': 'N', 'J': 'M', 'M': 'P', 'L': 'O', 'O': 'R', 'N': 'Q', 'Q': 'T', 'P': 'S', 'S': 'V', 'R': 'U', 'U': 'X', 'T': 'W', 'W': 'Z', 'V': 'Y', 'Y': 'A', 'X': ' ', 'Z': 'B', 'a': 'd', 'c': 'f', 'b': 'e', 'e': 'h', 'd': 'g', 'g': 'j', 'f': 'i', 'i': 'l', 'h': 'k', 'k': 'n', 'j': 'm', 'm': 'p', 'l': 'o', 'o': 'r', 'n': 'q', 'q': 't', 'p': 's', 's': 'v', 'r': 'u', 'u': 'x', 't': 'w', 'w': 'z', 'v': 'y', 'y': 'a', 'x': ' ', 'z': 'b'} (The order of the key-value pairs may be different.) """ ### TODO. assert shift >= 0 and shift < 27, 'shift %s is not between 0 and 27' % shift #numbers.Integral used in case of long integers assert isinstance(shift, numbers.Integral), 'shift is not an integer' coder = {}

lowercase_and_space = string.ascii_lowercase + ' ' uppercase_and_space = string.ascii_uppercase + ' '

# Shift letters over shift places shifted_lowercase_and_space = lowercase_and_space[shift:] + lowercase_and_space[:shift] shifted_uppercase_and_space = uppercase_and_space[shift:] + uppercase_and_space[:shift]

# Construct Caesar cipher dictionary # Add uppercase letters first so ' ' will be overwritten to point to lowercase letter for i in range(len(uppercase_and_space)): coder[uppercase_and_space[i]] = shifted_uppercase_and_space[i]

for i in range(len(lowercase_and_space)): coder[lowercase_and_space[i]] = shifted_lowercase_and_space[i] return coder

print(build_coder(3))

When I try to run this code it says number is not defined. How do I fix that so that I can run this code?