String validation (min, max, regex) in FastAPI - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set a minimum length of 3 for the username field.

FastAPI

from pydantic import BaseModel, Field

class User(BaseModel):
    username: str = Field(..., min_length=[1])

Drag options to blanks, or click blank then click option'

A3

B5

C1

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 or 1 which allows too short usernames.

Confusing min_length with max_length.

The min_length parameter sets the minimum number of characters allowed for the string. Here, 3 means the username must have at least 3 characters.

2fill in blank

medium

Complete the code to set a maximum length of 10 for the password field.

FastAPI

from pydantic import BaseModel, Field

class User(BaseModel):
    password: str = Field(..., max_length=[1])

Drag options to blanks, or click blank then click option'

A8

B5

C12

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Setting max_length too low, making passwords too short.

Mixing up max_length with min_length.

The max_length parameter limits the string length to a maximum number of characters. Here, 10 means the password cannot be longer than 10 characters.

3fill in blank

hard

Fix the error in the regex pattern to only allow lowercase letters for the nickname field.

FastAPI

from pydantic import BaseModel, Field

class User(BaseModel):
    nickname: str = Field(..., pattern=r"[1]")

Drag options to blanks, or click blank then click option'

A^[a-z]+$

B^[A-Z]+$

C^[a-zA-Z]+$

D^[0-9]+$

Attempts:

3 left

💡 Hint

Common Mistakes

Using uppercase letters in the pattern.

Forgetting to anchor the pattern with ^ and $.

The regex ^[a-z]+$ means the string must contain only lowercase letters from start to end. Other options allow uppercase letters or digits, which are not correct here.

4fill in blank

hard

Fill both blanks to create a field that requires a string with minimum length 5 and matches only digits.

FastAPI

from pydantic import BaseModel, Field

class User(BaseModel):
    code: str = Field(..., min_length=[1], pattern=r"[2]")

Drag options to blanks, or click blank then click option'

A5

B^[0-9]+$

C^[a-z]+$

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong regex that allows letters.

Setting min_length too low.

The min_length=5 ensures the string is at least 5 characters long. The regex ^[0-9]+$ restricts the string to digits only.

5fill in blank

hard

Fill all three blanks to create a field that requires an uppercase string between 2 and 6 characters.

FastAPI

from pydantic import BaseModel, Field

class User(BaseModel):
    tag: str = Field(..., min_length=[1], max_length=[2], pattern=r"[3]")

Drag options to blanks, or click blank then click option'

A2

B6

C^[A-Z]+$

D^[a-z]+$

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up min_length and max_length values.

Using lowercase regex instead of uppercase.

The field requires a string with at least 2 and at most 6 characters. The regex ^[A-Z]+$ ensures only uppercase letters are allowed.